Koi Pond Construction: The Basics of Building your Pond

Koi Pond Construction Basics

Section 1 – Choosing the location

One of the biggest challenges in constructing a Koi pond is finding the right location for it.

Having a koi pond that is either inaccessible or hidden defeats to the reason why you installed a Koi pond in the first place!

Here are some points you should consider when planning your koi pond installation:

1.)  Accessibility – you wouldn’t want your pond to be inaccessible and away from people. One of the great things about keeping a koi pond is it immediately brings delight to the people who see it. Having to go through several obstacles just to see your fish isn’t going to be convenient to guests that want to check out your pond.

2.) Visibility – the view of your pond should be largely unobstructed. One thing many folks do is plan for a dedicated viewing area.

3.) Cohesiveness – your pond should blend in perfectly with its surroundings, not stand out or be swallowed up by it. Your pond should look like part of the landscape. As a word of caution, be aware that shade is good for your pond and fish but putting your pond near/under trees will result in falling leaves into your pond that will decay and cause water quality issues.

One way to effectively visualize your pond for appropriate fit into your surroundings is to mark out the spot where you’re going to put it with spray paint. A bright orange spray should make it stand out so you can view it from different angles. Other folks will lay down string or garden hose to map out the pond.

Once you’re satisfied with the location of your pond it is the right time to start digging. Give it a couple of days or so before you pick up the shovel just to make sure you are 100% happy with the location.

Section 2 – Size and depth matter

Once you’ve decided where to build your pond, the next thing you need to do is determine how deep it will be.

Not surprisingly, you will need a larger pond for a greater number of fish but you will also want to plan for the increasing size of fish through the years.

For the average koi pond keeper, a pond 24 feet long by 12 feet wide with a depth of 4 feet should be sufficient for mid-sized koi. This depth will also allow for pond freezing in winter. This volume should be enough to accommodate ten 24 inch fish or twenty 12 inch fish without overcrowding issues. Another good rule of thumb for both aquarists and pond keepers is “less is more”.  More fish in a pond won’t necessarily bring you more happiness. In fact, more fish can sometimes translate into more maintenance and issues.

In order to calculate the volume of the pond you are wanting to build, use this formula:

Length (of the pond) x Width (of the pond) x Depth x 7.5 = Volume of water (in gallons)

or see this online calculator.

Section 3 – Everything falls to the bottom

Since your new koi pond is occupying a large space on your property, things are eventually going to fall into it. Leaves, dirt and other debris are going to find their way into your pond. And that doesn’t take into account all the fish food and droppings that are eventually going to find their way to the bottom of the pond.

This is where the bottom drain comes in.

Bottom drains in koi ponds are pretty standard and a four inch pipe leading out is optimal. Organic matter that falls to the bottom will eventually become pond muck. It will build up and make your pond stink which defeats the purpose of having a koi pond.

A bottom drain effectively sucks this all up, sends it into the filtration system for proper filtering, and disposes of it. The bottom drain is your first line of defense for muck build up.   The “old school” mode of thinking was to simply have a gravel lined pond bottom which, on the one hand is good because it allows for lots of surface area for beneficial (nitrifying) bacteria but on the other hand it allowed lots of muck to accumulate.   This resulted in the necessity for regular yearly (usually spring time) cleanings of the pond which involved draining the pond and removing all that slop. Very messy! The bottom drain will drastically reduce the amount of much removal and cleaning you will have to do.

bottom-drain for koi pond

Typical bottom drain

Tip: Be sure that your pond is not too close to trees as leaves are bound to end up in your pond and will not only be unsightly but can decay and throw off the chemical balance of your pond.

Section 4 – The Filter System

Achieving clean water is ensuring good koi health. For a koi, the pond is their entire world. That means they breathe in it, sleep in it, feed in it and eventually pass their wastes in. If you don’t have a pond equipped to handle the wastes, it could become very dirty in a short period of time and you’re going to end up with very sick and unhappy fish.

You need a proper filtration system to avoid this.

There are four essential components of a koi pond filtration system.

Bottom drain – we’ve already covered this in the previous section so you are already familiar with the function of this and why it is essential to your pond’s success. A 6000 gallon pond can function properly with just one bottom drain. A larger pond will mean installing another bottom drain to effectively clean your pond’s bottom (benthic) surface.

bottom drain and cross section

Settling chambers – the bottom drain typically dumps out at the settling chamber.  As the name implies, this is where heavier solids settle out and the pump then pulls water out of the top of the settling chamber, which then passes through mechanical and biological filtration and back to the pond.

settlement chamber

Settlement chamber

Mechanical filtration equipment – this is what filters out the bulk of the debris. This happens as particles are trapped in the brushes of the equipment. Since this will eventually get clogged you must make sure you buy the equipment that ensures you will always have replacement parts or brushes when it is time to replace them.   Mechanical filtration is usually set up in stages where coarse mesh material catches larger debris first then subsequent filters are finer mesh and sieve out smaller debris.

Biological filtration – this is the chemical portion of the filtration process. Ammonia and nitrites are ever-present in bodies of water where fish live. These are the products of their waste which need to be processed in order to make the water habitable. Your pond performs this biological filtration on its own to a certain degree but having dedicated filter media where beneficial bacteria can thrive and perform the important work of assimilating the harmful ammonia, nitrites and nitrates is crucial to the longevity of your pond.

As soon as everything is broken down, the processed water will go back into your pond, much healthier than it started. Testing for ammonia and nitrites should also be done on a regular basis to ensure that everything is functioning well and that your biological filtration is in good shape.

Tip: Some pond owners are confounded by sudden increases in nutrients -this can often happen after a rain storm to ponds that are near places like golf courses or farmland.

Section 5 – Time to bring out the shovels

 There are three primary ways to install a pond.

• Prefabricated mold (plastic or fiberglass)

This is the most expensive option but what you save is hassle. This system only requires that a hole be dug that matches the mold’s shape.

• Liner (vinyl or butyl)

This is probably the most cost efficient manner of creating a pond and probably the most popular method used by koi owners all over the world. It allows for a lot of customizing and you can really use your imagination with this material. What you save in cost is countered by the greater effort to install.

• Concrete

This is the most expensive manner of fabricating a pond but also the one that provides a lot of flexibility in terms of creating a pond matching your expectations. Though more expensive than the previously-mentioned methods it offers substantial strength and leak-proofing.   Another added benefit is that is helps to buffer swings in pH due to the carbonate in concrete and grout.

It helps to set out all of your materials so you know where your equipment is going to go when the pond is complete. Measure each piece so you know the actual dimensions and determine just how far you should dig. In the following example a pond is being built using a vinyl liner.

Excavate the entire area within your outline to about 9 inches deep. This should effectively set your pool area apart from the rest of the area and give you a better visualization of what it will look like in the end. Avoiding a perfect circle shape for your pond will help steer clear of the “necklace effect” which results in a “necklace” of rocks lining the pond edge. A better shape to shoot for is essentially an irregular shape that allows your pond to look more natural.

The next thing you should do is dig a trench along the outline you traced on the ground. A trench about 12 inches wide and 12 inches deep should be sufficient. This is going to be your initial shelf where your ornamental rocks will be positioned.

Place flat wooden stakes all around the diameter of the trench’s sides. This means both sides so you’ll have wooden stakes on the outer layer and the inner layer. This is where you are going to place your plastic shaper so that the cement you pour in is going to conform to the shape of the trench.

Before pouring the cement in, place some rebar to create a basic framework or support system for the concrete once it hardens. This will also allow the cement to retain its shape once this process is done. Tie the ends of the rebar together with some wire and then elevate them with a small block of cement as evenly as you can all throughout the diameter of the trench.

Now pour the cement in. Make sure that the volume of cement per feet inside the trench is consistent. After that, use a wooden planer to level out the top of your cement.

Allow for the cement to harden before moving on to the next step which is to remove the plastic shapers and continue digging out the hole. The cement should be ready after letting it sit for about 24 hours.

After that process is done, you can excavate the area interior to the concrete. With the cement bench in place, you should be able to excavate as vertically straight as possible along the edges.

With respect to depth, a good depth should be around 4 to 5 feet. It’s deep enough for the fish to have some variety in terms of swimming depths, thermal refuge during winter and shallow enough for the average person to get into to provide preventive maintenance care on a regular basis.

Make sure the bottom of your pool has a gradual slope towards the center of your pond. This is where you’ll be installing your bottom drain. Another thing to note is that if you live in an area cold enough to cause your pond to freeze over you will want to angle the sides of your pond in (towards the pond center) around 15 degrees to allow for the expansion of ice to slide along the angle and not outward against the liner.

The next step is install the bottom drain and anchor it at the lowest part of your pond. You will need to dig a deeper hole to set the foundation of the bottom drain and a trench for its pipes to run through. And then you will have to anchor it down so there is no unwanted movement which could compromise the fittings of the pipes. This movement is usually caused by water pressure from all the water movement.

The next thing you need to make sure of is that you have the proper returns and fittings installed for the pump and filtration system. One great thing about the filtration system is that you can elevate it and hide it with some strategically placed rocks to emulate a waterfall. This should help you create a waterfall effect. Your returns on the other hand can be placed in several locations to create several vortices to direct the water flow.

Another important addition for your pond is a skimmer to keep the surface of your water looking great and to keep floating debris like leaves from ever making it to the bottom to decay.

skimmer box

Skimmer Box

Whether you have a sunken pond or a raised fish enclosure, it’s always best to keep your liner and plumbing hidden from view. Nothing is more unsightly than exposed plumbing and liners. But there’s another reason why you should hide these from view. Since your pond is essentially going to be an outdoor fixture, it is going to be exposed to the elements. Your liner and plumbing which is made of a plastic and vinyl mixture is eventually going to be damaged over time and either crack or warp.

Remember the shelf you made with the cement? This is where your liner will rest being held in place with rocks over the edges. Do not cut the edges of your liner until you are absolutely sure that everything is set and in place. You will want to lay down a layer of sand or something that will help cushion the liner from possible puncture prior to setting in the liner.

Another thing to be aware of is to ensure that the edge of your pond is slightly higher than the surrounding areas to prevent rainwater from flowing into the pond. An elevation of an inch or two should suffice unless you live in an area that gets plenty of rainfall. 

Basic Pond Construction with Liner

Final Thoughts

The methods and techniques presented here are typical and used successfully by many however it should be noted that there are LOTS of ways to build a healthy pond. There’s lots of ways to filter water and not just one, tried and true method. For example, some folks don’t have bottom drains, some folks would never consider using a liner while others swear by it. Your particular situation and finances will dictate what kind of pond you install and the size of your filtration you need.   Beyond the foundation of your pond, the components you want to put the most energy and investment into is your pump and filtration because those are your heart and kidney’s of the pond.




Posted in Pond Equipment | Tagged bottom drains, concrete liner, fiberglass shell, koi ponds, pond construction, pondliner | 4 Comments

Understanding Koi Pond Filtration

Pond Filtration: the basics of koi pond filtration


Koi Pond Filtration: The Basics

Koi ponds and koi keeping are gaining popularity in the U.S. and in many parts of the world. Koi ponds are as varied as the places they are found. Ponds can be deep or shallow, be natural or constructed with liners or concrete but no matter what form they take the filtration system of the pond will always be universally vital to the health of the resident fish. If you are unsure where to start when it comes to understanding a koi pond filtration system, this article is meant to give you an overview and a place to start.

pets by popularity

Ranking Pets by Popularity

Koi produce waste that could be classified as both chemical and physical so as you can imagine it only makes sense that your pond will need to have the ability to handle both. The two main types of filtration are biological and mechanical. Biological filtration cultures aerobic (nitrifying) bacteria that will help break down the chemical components of fish waste. Mechanical filtration is employed to handle the physical waste like fecal matter, dead leaves, dead insects etc.

Setting up your Pond

There are specific elements you need to have present in your pond to ensure the health your Koi. Before delving into filtration, you should have an understanding of the basic components of the pond and their purpose.

Bottom Drain

Most ponds will have a bottom drain. For the sake of the natural path of debris and waste that falls to the bottom with gravity, the bottom drain is often positioned at the deepest point of the pond.   Ponds without a bottom drain will have to deal with wastes building up and causing muck that will have to be removed at a later date (like every Spring) or regularly vacuumed out. The bottom drain will lead to a settlement tank. The water flowing into the bottom drain will move into a settlement tank, which is then allowed to settle to the bottom of the tank while the surface water is sent towards the pump. In between the tank and the pump will be a filter, such as a bio filter. This filter helps remove more waste from the old water, ensuring cleaner water is then pumped back into the pond.

You will need to ensure the flow rate of the water matches up the bottom drain pipe size. A slow flow rate will cause the heavier particles to settle in the bottom drain piping instead of moving into the settlement tank. However, you need a flow slow enough that it allows heavier waste to sink while in settlement tank. To help you figure out the proper bottom drain configuration, consider a three inch bottom drain, which is able to sweep a 4 foot radius. In order to work, this drain needs a minimum water flow of 1500 gallons per hour, so the sediment will not settle in the piping. It is better to have 2,500 gallons per hour with a 150 gallon settlement tank when using a three inch bottom drain.

A four inch bottom drain is ideal and can sweep a six foot radius and requires at least 2,500 gallons per hour for a 250 gallon settlement tank. In order to ensure that your settlement tank will do its job properly, a good rule of thumb is to match your settlement tank volume to your minimum water flow at a value of 10% -in other words, your settlement tank volume should be about 10% of your gallons-per-hour water movement.

bottom-drain for koi pond

Typical bottom drain

Gravity obviously does a lot to get the sediment and waste into the settlement tank. Once the water is in the tank, the solid waste will remain unable to move beyond the tank until the pump suctions off the settlement tank.

The settlement tank will require a little help from you. While most of your pond can be kept clean with the bottom drain and skimmer, there is also a need for some maintenance. You should get into the habit of checking the settlement tank filter every other day or so. The waste container will fill up and needs to be dumped. It is your job to make certain this happens on a regular basis.


The bottom drain, as the name implies, is at the bottom of the pond however another form of filtration often seen in ponds is the skimmer. Skimmers are your other mechanical filtration system. The skimmer works on the top of the pond collecting floating debris such as leaves, grass, pollen and the like. The skimmer will pull from across the top of the pond collecting waste, filtering the water back to the pump. Ranking those two systems in order of importance, the bottom drain would certainly be first. Floating debris will effectively be removed via the skimmer, but without it all things would ultimately make it to the bottom drain.

The skimmer also removes dissolved organic compounds. If you do not have a skimmer, the surface of your pond may end up with an oily film, which will reduce the ability of atmospheric oxygen to diffuse into the pond via the water’s surface.

typical pond skimmer

Typical Pond Skimmer

The skimmer has a weir or a floating device that floats up and down with the water level. It skims only the surface of the water. If building a new pond you want to get the widest weir available, at 16 inches, to help clean the pond surface area quicker. The skimmer also has a “leaf basket,” which collects the large debris. Some skimmers may have netting or mats, but it works the same way. It ensures the debris cannot cloud the surface of your pond or get into the pump.

Mechanical Filtration

This type of filtration is one of two main kinds of filtration going on in your pond. At its simplest, fish produce both liquid and solid waste which represents both a physical addition and chemical addition to the pond. As a result, a pond owner needs both physical and chemical means of removing these wastes from the pond. Of course, there are other sources of nutrients like rainwater runoff, decaying plant matter, dead insects etc. as well as other sources of solid wastes like dead leaves, branches, pollen etc. Additionally, those solid wastes come in different sizes and need to be filtered out accordingly therefore a good mechanical filter will have multiple stages. Typically these stages are set up such that water carrying particulates pass through the largest pored filter material first then gradually each stage’s pore size gets smaller to trap smaller particulates. Let’s look at a typical multi-stage mechanical filter.  As you can see from the image, as the water enters it is met by coarse filtration, then finer filtration, and then even finer filtration etc. until making its way to biological filtration.

example of mechanical filtration

Biological Filtration

The biological process of beneficial (nitrifying) bacteria assimilating nitrogenous waste is natural and occurs in the wild, as well as in your own pond. When your fish produces waste it eventually turns into ammonia, nitrites and nitrates. If there is an improper biological filtration in your pond, it can leave your pond with an excess of these waste products which ultimately reaches a point of toxicity—killing your fish. Biological filtration is an aerobic process, meaning oxygen is involved. Ammonia is broken down into nitrites. A second type aerobic bacteria will take the nitrites and break it down into nitrates. At low levels, nitrates are harmless to your fish but regular water changes are also a good idea (assuming the volume of water changed out is small enough that is doesn’t cause signigicant pH swings).

The name of the game when it comes to setting up your biological filtration is surface area.   There are varying approaches to achieve high surface area filter media and these include porous rocks, ceramic rings, bio-balls and other plastic shapes that yield a high surface area.   So why all the need for surface area?   A few beneficial bacteria assimilating your pond’s nitrogenous waste is good but a lot of bacteria is great so having a lot of surface area for these bacteria to live and thrive means that your biological filtration is that much more powerful.

For biological filtration, you want an oxygen rich environment so that the aerobic bacteria are able to assimilate the nitrogenous waste as efficiently as possible. To ensure this happens you need a pond with a large surface area and plenty of supplemental oxygenation via waterfalls, fountains, aquatic plants or diffusers.

When considering the right filtration system for your pond you will want to keep in mind that the entirety of your pond’s volume should be filtered every hour so choose a pump capacity/speed and filtration that will meet that goal. Let’s now take a look at some of the popular filtration systems to give you an idea of what’s out there and how they look when set up.

External Pressure Filters

The external pressure filter system is a common one and typically consists of an intake in your pond (usually sits on the bottom) that draws water in then up through a line, out of the pond and into the pressure filter itself. There are many different designs in the world of pressure filters but essentially you will find some manner of mechanical filtration (usually in the form of a sponge-like material) which then leads to biological filtration (usually in the form of bio-balls) then out of the filter. Some manufacturers will also have a UV light installed such that the water exiting the pressure filter passes by the UV prior to leaving the filter. From the filter it will often enter back into the pond via a water fall. They are nice systems that can be hidden out of sight either in a false rock or in an accessible, sub-terranian compartment. As with any filtration system outfitted with mechanical filtration you will have to periodically rinse off the sponge material catching the particulates. See the diagram below for the typical set up on these style systems.

submersible pump plus external pressure filter



The all-in-one systems like the Lifgard Aquatics example shown are often submersible units that have the mechanical filtration, biological filtration, UV clarifier and pump all in one compartment. So in the given example, this unit has an extended neck that then directs the filtered and clarified water into the fountain feature thus aerating the water.

lifegard all-in-one filter (triple)

Multi-Stage Compartment Filters

These filtration systems are external and designed quite simply. Its essentially a plastic box with mulitple sheets of filter media arranged in a pattern of coarse to fine. Some units, like the Matala Biosteps series, will have a UV clarifier in the first compartment before going through the stages of filtration.   Other manufacturers will put bioballs as the last stage however the 4 staged filter material in the Matala are also meant to act as substrate for the beneficial bacteria to colonize. Cleaning units like this is a simple matter of shaking off any debris clogging the filters, allowing it to settle to the bottom then purging the waste out through the bottom drain. In the case of these progressive, multi-stage filters the water drawn through the system is either pumped from a submersible at the bottom of the pond or an external pump draws it up from the pond.

matala biosteps 10 filter

Ultraviolet (UV) Filtration

A somewhat newer addition to the koi pond filtration arsenal is the UV sterilizer/clarifier. The UV filter has been mentioned on multiple occasions in this article as it has gained increased popularity over the years. You’ll see a lot of different filtration systems with UV as part of the package as well as in-line UV sterilizers and clarifiers too. In essence, what happens is that pond water is passed over/near a UV light source and the ultraviolet light energy effectively disrupts the chemical bonds that bind the microorganism’s DNA together. As as result, the bacteria, virus, protozoans, algae, or mold effectively die.

In any given drop of pond water, there may be thousands and thousands of bacteria and viruses.

The cool thing about UV is that is leaves no chemical residue or impurities in the water.   Its just light energy that is strong enough, and at the right spectrum, to kill microorganisms and requires only a bulb change when it becomes too weak to kill. The UV sterilizer/clarifier is typically placed before the mechanical filtration as it tends to cause free floating algae to clump together.

UV sterilizer vs. UV Clarifiers

The difference? Well, not much. Clarifiers go as far as killing free floating algae that causes green water whereas a sterilizer gets at the other nasties in the pond such as viruses, bacteria, protozoans etc. A single in-line UV light for a small pond might be a sterilizer whereas that same light at a pond 3 times bigger might be considered a clarifier. It really comes down to wattage (strength) and flow rate (which will dictate how long the water gets exposed to the UV light). Other important factors are your biological load already present in the pond. Do you have lots of fish or an appropriate amount?   Do you already have natural filtration going on in the form of aquatic plants? What is the volume of water in your pond? Big ponds need stronger UV exposure. To determine what your pond’s needs are its simply a matter of taking into account several key factors and using the chart below as a general guide.  

UV bulb sizing chart

UV balasts and bulbs are not necessarily cheap so is it worth it?   Viruses and bacteria make up a large proportion of health problems in any given koi pond. Many koi pond problems stem from water quality issues which then translate into koi health problems as well as algae blooms. Fortunately, UV kills green water (free floating) algae which can infest your pond, die then cause a spike in nutrients and a drop in dissolved oxygen.

One bacteria, under ideal conditions, can turn into 1 billion bacteria in a matter of 10 hours.

There is even a “major trend in swimming pool technology” being seen across the U.S where UV is being used in more and more pools which underscores the effectiveness of UV to kill unwanted, water-borne microorganisms. So the cost up front may very well save you plenty of money and headaches down the road.

Ion Filtration

Even newer than UV is the use of Ion Filtration. Its a compact, easy to set up system that effectively kills free floating algae, viruses and bacteria. The way it works is this: a flow chamber containing two anodes (elongated, rectangular metal blocks) have a low voltage current going to them.   The anodes are made of copper, silver and zinc (though some are just copper and silver). When there is an electric charge applied to the anodes they give off billions of positively charged ions of silver and copper.   Because unwanted things like algae, fungus spores, viruses and bacteria are negatively charged they are attracted to the positive ions. The copper ions are able to damage the cell walls enough that the silver ions get in there and destroy the cell. Because the electric charge is so minimal and localized to the in-line ionizer in your pipes there is no adverse affect to your fish nor is there residual copper or zinc in tests of the water. Also because it draws such little power its very inexpensive to operate. The anodes will eventually become worn out and require replacement every year or so.

Aquascape IonGen ionizer plus diagram

Ozone Filtration

Disinfection of water via ozone has actually been around since the late 1800’s so its not surprising to see it in use in koi ponds (or where ever water needs to be sanitized). Ozone is arguably the most powerful destroyer of bacteria and viruses in the world of aquatic disinfection. In fact, its 50% more powerful than chlorine and yes, it kills algae cells too. As with many forms of filtration mentioned above, there is no residue left over. In fact, the water is left super clean and more oxygenated because ozone breaks down into oxygen. Furthermore, only ozone can break down hydrocarbons like derivatives of oil and gas.   So how does this all work?

Air is passed through the Ozone generation mechanism where electric current is applied resulting in the creation of ozone gas. This gas is them pumped into a special chamber where it is allowed to diffuse into the water. Immediately hydrocarbons, viruses, bacteria, and other pathogens are destroyed and the action of ozone destroying these unwanted nasties converts it (ozone) back into oxygen thereby further oxygenating the water. Your fish never come in contact with ozonated water as it all takes places in a sectioned off area or a special chamber.

Natural Plant Filtration

Possibly the easiest filtration to implement in your pond is the oldest kind…aquatic plants. They are the gift that keeps on giving…and they grow and multiply. Besides the important filtration work they do naturally they also provide shade for your koi as well as substrate for female koi to attach eggs to. They also add dissolved oxygen to the pond as well. Depending on your pond’s design you can install submerged plants, floating plants or plants partially submerged that sit on a shelf or shallow area.   Some favorites among pond owners are water purslane, fanwort, American Waterweed, iris, lotus and lilies. You will have to match the plants you get to your climate zone and pond design but aquatic plants add a great deal of functional value as well as aesthetic value to your pond.

koi pond cut away how pond plants benefit your pond final 3

Besides the aesthetic beauty of pond plants there are many other benefits to your koi pond


The aim of this article was to give you a good place to start in understanding koi pond filtration and all the different ways your water can be filtered to give your koi the best environment possible.  No one pond will have all these types of filtration but it will be up to your situation, space and finances to determine what filtration system(s) is going to be the best fit for your pond.  No matter how you slice it though, filtration is important so make sure you put the kind of time and effort into it that it deserves -your fish will thank you!

Posted in Pond Equipment | Tagged aquatic plants, biological filtration, bottom drains, Ionization, koi pond filtration, mechanical filtration, nitrifying bacteria, ozone, settlement tank, skimmer, UV | 6 Comments

“Chilled Out” Koi: How Koi Survive Frozen Ponds in Winter

 Koi-under-ice-web-copy 2

If you live in a northern climate then chances are good that you see snow and ice as does your koi pond.  Its natural to worry about your koi during the winter periods, especially if they have been around for years and years.  Fortunately, koi are adapted to dealing with cold temperatures and an iced-over pond.  They have a few tricks up their “sleeves” to deal with the inevitability of ice cold water. 


Regulating Body Temperature

Thermoregulation of animals or how an animal regulates its body temperature can be a confusing subject.  For example, within the subject of thermoregulation there is:
– Ectothermic
– Endothermic
– Mesothermic
– Heterothermic
– Homeothermic
– Poikilothermic
– “Cold-blooded” 
There’s a lot of variations in the world of temperature regulation in animals but to make it more straightforward for koi owners you should know that your fish are ectothermic,which means that their internal body temperature is governed strictly by the ambient temperature (or in this case, the water temperature).  So that must mean that all fish are ectotherms, right? Not necessarily.  Unfortunately, biology is not always consistent.  For example, the bluefin tuna and some sharks create internal heat from muscle activity yet are still largely affected by water temperature which puts them in a category known as mesothermy.  Furthermore, the term “cold-blooded” is actually not all that accurate.  A “cold-blooded” lizard in the hot desert sun can achieve an internal temperature greater than that of humans.  So in everyday conversation its just easier to refer to mammals and birds as endotherms and just about everything else as ectotherms.

Biological Activity and Temperature

You have probably noticed throughout the seasonal changes that as the water temperatures get colder your fish start to become less active.  As a result, they require less food and at somewhere between 50 and 40 degrees F they stop eating all together.  Ectotherms are able to pull this off because they don’t have to maintain a certain internal temperature and, in fact, they can get away with using as little as 10% of the energy of what a mammal would need.  As temperatures fall, the rate of internal biological activity decreases which includes things as basic as how fast a muscle can twitch.  This concept in biology is known as the Q-10 coefficient. 

Planning for Winter

There’s not much activity going on with your fish, on the inside or outside.  They don’t need food and not as much oxygen however its still a good idea to keep some of your pond unfrozen with a de-icer for gas exchange (and some pond owners will run aeration all year long).  One of the things your koi will do is try to hang out in the warmest part of the pond and that will subsequently be the deepest part.  In general though, its a good idea, when designing/building a koi pond, that you make it at least 3 feet deep to avoid the possibility of total pond freeze.  Another thing you may want to keep in mind is that adding salt to your pond before winter will lower the freezing point of water and artificially cause your water to reach a super low temperature which can potentially harm your koi.

Koi in Dormancy

So what exactly are they doing under the ice? Sleeping? Playing cards?  As with thermoregulation there are a lot of different ways to go inactive during winter (or periods of less-than-ideal conditions).  There is:
hibernation in mammals
brumation in reptiles
diapause in insects and
aestivation in invertebrates
but ultimately your koi under ice are in a state of dormancy.  Essentially, they are simply “chilling out” in a state of super decreased activity and metabolism while waiting for spring.  Perhaps you don’t get to enjoy your koi as they mill around under the ice but just think of the money you are saving not buying koi food!
Posted in General Koi Information | Tagged aeration, de-icers, dormancy, frozen koi ponds, gas exchange, less activity, no food, survival | 9 Comments

Feeding your Koi as Water Temperatures Change

Everyone knows that water temperature plays a big role in how active koi are but a koi’s metabolism and ability to digest certain types of foods are also affected. Its critical that as temperatures drop with approaching winter or as temperatures increase with the onset of summer that you feed your koi the right amounts and at the right time. To illustrate some of the more important points of koi feeding schedules and how the are tied to water temperature I’ve created this infographic:

Koi Feeding Temperatures

(Click image to enlarge)

In addition, later this month I will be following up this infographic with a helpful chart on koi length, age and size so help you better understand how your fish grow.

Posted in Food and Nutrition | Tagged feeding, food, healthy koi treats, koi foods to avoid, recommended foods, water temperature | 14 Comments

Quarantine Your Koi: Why and How

Quarantine Tank Diagram (web)

Anyone that has cared for or owned koi for any significant period of time has had to isolate their fish for one reason or another. Sometimes its necessary to remove your fish in order to clean their pond or perhaps there are signs of disease that you want to prevent the further spread of -whatever the reason, having a quarantine tank is a necessary component of your koi pond “system”. Quarantine is a great way to isolate your fish in times of stress or times when you want to control which breeding pairs you want to match up. Of course, one of the main reasons for having a quarantine tank is for situations where you suspect your fish is diseased but one thing some koi owners neglect is using it for newly arrived, healthy-looking fish.

Types of Quarantine Tanks

For some, a smaller glass-style aquarium quarantine tank is all that is required when koi are small. Later, when your koi grow too large for glass aquaria a commonly used container is the fiberglass or Rubbermaid tub style. These are nice due to their cost, low weight and versatility. The fiberglass and Rubbermaid tubs can be found at many different retailers but probably the most convenient source will be farm supply and feed stores. If they don’t have the size you need they can find it and order it for you.

Must have’s for your Quarantine Tank

One of the biggest questions that koi pond owners will have when considering setting up a quarantine tank is: “how big does it need to be”? To answer that you first need to consider how large your fish are currently and obviously how large they are going to be. It’s always convenient to plan ahead for when your fish get to be older and larger (which is when you are really going to want to make sure the quarantine tank does its job). As a rule of thumb if your fish are in the 10-11″ (3.9-4.3cm) range look for a quarantine tank that is at least 200 gallons (757 liters). Your quarantine tank needs to have biological filtration. There are some pond owners that don’t think about this because they often don’t keep their fish in quarantine for long enough so they may only have aeration. To do it right the quarantine period should be at least 3 weeks but a full month is better. As mentioned, having plenty of aeration is critical to keeping your fish happy during the quarantine period. In addition to aeration you will want to keep the tank out of direct sunlight. As is the case with your main pond, you provide means for shade via tree canopy or aquatic plants so your quarantine needs to have shade as well. Lastly, it’s important that you effectively prevent your fish from getting spooked and jumping out. This is done with a simple framed screen that fits over the top of your tank. Not only will it keep fish from jumping out but it will keep predators like raccoons and herons from preying on your recovering fish. Another thing that is nice to provide for your fish is something to hide in or near in your quarantine tank like a large PVC pipe or something similar.

Transferring and Maintaining Koi

Whenever you bring a new fish home from a breeder or need to transfer a fish from your main pond to the quarantine tank it’s critical that you ensure the fish has adjusted to the new water temperature (and this is especially true when going from warmer to colder water). A lot of times small koi that you buy will be in clear bags so simply placing the bag on the surface of the tank and allowing the water inside the bag to match that of the tank will suffice. However you choose to make the adjustment be sure it’s gradual -you don’t want to do more harm to a sick fish you are trying to save.

Once the fish has been transferred you will want to wait at least a day before attempting to feed your fish. Oftentimes because of the stress of moving fish won’t eat for a day or two anyway.

How long should you maintain and treat your koi in quarantine?

The treatment, depending on what it is, may actually only be one day but that doesn’t mean your fish is ready to go back to the main pond. You will want to ensure that the fish is good to go and is not showing any signs of the malady so it is recommended that you keep your fish in quarantine for 3 to 4 weeks. A mistake that is often made by koi owners is taking a recently purchased fish and putting it straight into the pond. Though it may look healthy it may also have some healthy parasites that would love to have access to a big pond full of unsuspecting koi. It’s always a good idea to quarantine anything new for 3-4 weeks and watch for signs of disease or parasites (and periods longer than 4 weeks are not unheard of for certain kinds of parasitic infestations).

Creating the Right Conditions

Something a lot of pond owners will do for newly purchased fish that in quarantine is to maintain a raised salinity level to offer osmostic relief to the fish and deal with certain parasites that may be present. For these purposes a level of 2-3 pounds of salt per 100 gallons is a good level to maintain. You will also want to do regular water changes as well. If you are able to tend to the quarantine tank on a regular basis a 10% change out every other day is recommended but if once a week is all you can do then a 25-30% change out should suffice. Doing water changes will give you a chance to vacuum out any uneaten food or feces that may have accumulated on the bottom. For recovering fish, a temperature of around 76-77 degrees F is recommended which may call for a submersible heater to be used -a 250 to 300 watt heater should do the trick. And finally, as with your main pond, water quality needs to be monitored and tested regularly.



Posted in Koi Diseases | Tagged diseased fish, hospital tank, koi, proper size, quarantine, transferring fish | Leave a comment

Why Algae Occurs and How to Get Rid Of It

string algae koi-care.com

String Algae

It is the case that every spring, as temperatures rise and daylight hours increase, an algal bloom occurs in almost everyone’s koi pond.  Dreaded algal blooms, like green water that make koi disappear from view or unsightly string algae that seems to pop up from nowhere, seem to be an inescapable fact of pond life. 

There is a lot that happens during the transition from winter to spring.  One thing that many koi owners experience is an increase in disease.  This increase is, in part, linked to the fact that little beasties like parasites are doing well in the increasing water temperatures but a koi’s immune system is still coming back into full strength so there is a period in the spring when they are more vulnerable.

Additionally, the increase in temperatures, sunlight and available nutrients from dead and decaying plant material and fish waste act to fuel algal growth and a bloom occurs.  But what about the beneficial bacteria in the filter media?  

They are still there but, like a koi’s immune system, are not at full strength yet (more on beneficial bacteria later).  Algae are pretty simple as living things go.  They need sunlight, carbon dioxide (given off from the gills of respiring koi and atmospheric CO2) and nutrients (nitrates, phosphates, ammonia  etc.). 

There is more to the story though when it comes to what algae need and how well they will do.  Algae do well when pH is on the higher side and this is because certain nutrients are more readily assimilated by the algae under these conditions. 

Algae also thrive under conditions of stagnant water or decreased water flow (you’ve probably noticed that stagnant ponds tend to harbor a lot of algae).  Different algae behave differently though- read on for the characteristics of the most problematic types.

Two main types of algae

1) Phytoplanktonic (free floating) which includes types that cause “green water” or “pea soup” water conditions. This type of algae may be the most common to afflict pond owners.  Spring is often when ponds turn into what appears to be a large vat of pea soup-certainly not how koi keepers want their ponds to look. 

Besides being a spring bloom occurrence, this single celled algae is often associated with newly established ponds as well due to the fact that the filter hasn’t had time to establish a sufficiently large bacterial population yet.


Green Water Algae

Green Water Algae


2) Benthic (attached) which includes “string algae” or “horsehair algae”, “water net” and “blanket weed”. String algae can be a tough one.  This algae can remain dormant for years in a dried state until introduced to water after which it will thrive. 

Another problem is that when you manually remove it from your pond (which is the best way) the action of removing it causes it to release reproductive spores into the water and the cycle starts again. 

As string algae tends to produce a good deal of dissolved oxygen it tends to aggregate bubbles tangled in its “hair” and before long a big, unsightly mat of the stuff floats to the surface further reducing the beauty of your pond. 

Of course, something that produces dissolved oxygen in your pond is a good thing, right?  Yes, up until the point that it dies, sinks to the bottom and is broken down by bacteria that use oxygen to do so thereby depleting your pond of dissolved oxygen.


string algae mat

String Algae Mat



Algae Box-what algae needs to grow


The following is a list of ways to prevent algal growth in your pond.


Sunlight is a big component that is necessary for algae to thrive so by shading your pond in some way you can effectively reduce some of the potential algae fuel entering your pond.  One way you can do this is the old fashioned way- trees.  Try planting trees that provide canopy overhead near your pond. 

Besides aerial shade there is also the aquatic kind.  Pond owners have, for a long time, installed aquatic plants like lilies in their pond to not only create shade but they make your pond more aesthetically appealing. 

The “magic” number to shoot for when it comes to aquatic plant coverage is 60-70% surface coverage.  Another way to reduce light penetration is through non-toxic coloring agents (dyes) that essentially tint your water a certain color and reduce the available light in your pond.  

This has become a “go-to” solution for plenty of pond owners.  They typically last a long time and you have a few dye colors to choose.  If you reduce the sunlight penetration you reduce algae’s ability to thrive!  Here are few good dye choices to check out.

Reduce Nutrient Loads

Nutrients like nitrates and phosphates are key to algal growth so by reducing and nullifying these components you can severely limit algae’s ability to grow.  This is achieved by not overfeeding your koi, by keeping close tabs on water chemistry and making adjustments as needed. 

Make sure your pond isn’t subject to fertilizer runoff as that will often carry a lot of phosphates.  Be sure you have plenty of filtration and beneficial bacteria to assimilate nutrients etc.  You may also need to perform several water changes in an effort to reduce nutrient loads. 

If this is the case be sure that the water changes you do are gradual to ensure that your pond doesn’t undergo a significant pH swing as this may cause harm to your koi.  For more on how biological cycles work see this article.

Adding Salt

Salt seems to be a go-to remedy for a lot of things in the world of koi keeping and it turns out that it can help control algae blooms as well.  There is a caveat with using salt to combat algae in your pond though and that relates to the fact that high enough salinities will also harm or kill your aquatic plants. 

For example, common plants like water hyacinth and lotus will begin to die back at 0.10% whereas water lily won’t die off until 0.5% and to deal with algae effectively you will want to shoot for 0.25 to 0.30%.  You will have to determine if salt makes sense for your algae problems based on your resident species of aquatic plants.  

A good way to determine the right amount of salt is to the use koi-care’s online calculator and once added a simple way to check your salinity is with a commonly used tool called a refractometer.

UV Sterilizers    

One of the most effective ways of combating single celled algae like that which causes “green water” is an in-line UV sterilizer as part of your filtration system.  Its an excellent and non-invasive way of dealing with certain types of algae (and harmful bacteria for that matter) that can easily be added to your existing piping.  So how does UV light kill algae?  UV is a powerful kind of light energy and it effectively penetrates the cell membrane on the outside of the algae cell and hits the areas of the algae where the DNA is (nucleus and chloroplast).  Once this happens, the DNA gets so disrupted by the UV that the algae cell cannot reproduce.

How UV kills algae 

UV Clarifiers are also an option  if you are just targeting free floating algae but its less powerful (algae requires less powerful UV to be killed) so if you are going have a UV system you might as well have one that is going to kill other microbes and bacteria, too.  For most ponds a 30 watt system should suffice but be sure that the light you are getting is rated for the number of gallons you have.

Beneficial Bacteria

Besides UV sterilizers one of best things you can do for your pond is adding additional beneficial bacteria.  This is especially true during spring time when your filter media is not ramped up like it would be in summer. 

One of the more popular products on the market for getting your bacteria populations up is called Microbe-Lift PL and they even have seasonal “blends” depending on your needs (and season).  

Its generally a good idea to give your bacteria a boost from time to time but when it comes to algae you may find yourself in a cycle where the algae dies (either naturally or via algaecides), it decomposes on the bottom and causes high levels of nutrients like ammonia and nitrates and those nutrients then fuel the next generation of algae. 

Adding the beneficial bacteria will allow the nutrients to be assimilated before they become available for more algae thereby starving out future algal growth.  

Koi Clay

Koi clay is one of those additions to your koi pond that can only help.   This “stuff” is a natural way to add a lot of great minerals to your system and koi seem to love it.  As a side effect it has been reported to really be effective at inhibiting and killing string algae. 

It is a calcium bentonite clay and when added to your pond it will temporarily cloud it up.  It clears up in a day and will have added lots of beneficial minerals and removed toxins.  It is said that Kentucky produces so many great race horses because they eat the grass growing in Kentucky’s particularly calcium-rich soil.

Similarly, Japan’s koi might be so revered because of the clay rich ponds in which they are raised.  There’s lot of great koi clays on the market but you want ones that don’t remain cloudy for extended periods.


Barley Straw


One algae treatment you may have heard about but is perhaps a bit unexpected is barley straw.  You can get it as raw barley straw or its extract.  This treatment for green water can take up to 30 days to really get going and the results can be hit or miss.  

Some speculate that the barley straw works by breaking down and releasing a toxin that prevents algae while others suggest that the break down process produces hydrogen peroxide which creates a poor environment for algal growth. 

According to Rutgers University no one actually knows how barley straw prevents algal growth but its important to note that it prevents algae, it doesn’t kill existing algae so it shouldn’t be used as an algaecide.  This treatment is more effective on free floating algae as opposed to string algae and is typically used in the spring time. 


Chemicals for Treating Algae


Most algaecides can be placed into one of three categories: potassium permanganate-based, copper-based and simazine-based.  Simazine is a commonly used algaecide.  The way this chemical works is by disrupting the photosynthetic process and thereby killing the algae.  Caution should be used with this chemical as it can harm or stunt the growth of your aquatic plants (as they use photosynthesis, too).   

Potassium Permanganate

Use potassium permanganate with caution.  Not only is it used for parasites like costia but will also readily kill algae however you need to monitor the pond after you add it.  The dose should be something around 1 teaspoon per 1000 gallons to start but you may end up adding more or doing more treatments based on your needs and how much algae you have. 

You will need to double up on your pond aeration as you will see a lot of your fish come to the surface and gasp to get air.  Keep up the treatment for about 8 hours and make sure the treated pond water doesn’t go through your filter media as your beneficial bacteria will be killed off. 

Potassium permanganate will get used up as it kills the algae and parasites etc. so you won’t have to do a big water change as you would if you added a lot of salt.  It would be very helpful though to vacuum the bottom of your pond after the treatment is over and your fish aren’t showing signs of stress.

Algae Fix

Algae fix can be placed in the “copper based” category.  Most copper based algaecides are in the form of chelated copper (which lasts longer than other forms).  It can be effective as an algaecide because it disrupts algae cell metabolism however as with most treatments there are some precautions to be aware of. 

Vascular plants like water clover won’t be affected by the copper but other plants that derive nutrients from the water itself may be negatively affected.  The other thing to consider is copper’s affect on invertebrate organisms like snails and crayfish.  Because most invertebrates have copper-based hemolymph (blood) copper-based treatments will harm or kill these organisms.

Green Clean

One of the newer products on the market, “Green Clean“, kills algae via oxidation and results are very rapid.  There is no residue and it is not copper based.  Though it is advertised as a “broad spectrum” algaecide users have reported that it is best for string algae and not ideal for green water (free floating) algae.  The company provides a helpful demonstration video here. All the Green Clean material is in the first 4 minutes.



Accu Clear

This solution is in the family of treatments that cause green water algae to flocculate (suspended materials form small clusters and sink to the bottom).  The idea is that your filter will take care of the rest but as mentioned previously if you don’t vacuum the bottom afterwards it’s a good idea to pump up your beneficial bacteria populations to handle the excess nutrient fallout from the decay of the algae.  


Every pond owner will, at some point, have to deal with algae.  Typically people will struggle with it during the springtime when temperatures rise but fortunately there are plenty of go-to solutions. 

There are some that are broad spectrum and some that are will target one kind of algae or another.  The solution that is right for you is the one that meets your particular needs.  There are plenty of algaecide chemicals available on the market today and a lot of pond owners will attest to their effectiveness.

However, if you find yourself overrun by algae and don’t know where to start try some of the solutions found under “Prevention” in this article first before adding chemicals. You may have to go the chemical route though and if you do be sure to couple those treatments with some of the preventative measures talked about or you may find yourself in the same situation before too long.

Posted in Algae Problems | Tagged algecide, barley straw, beneficial bacteria, blanketweed, copper, free floating, green water, horsehair algae, koi clay, koi pond algae, pea soup, potassium permanganate, salt, simazine, string algae, UV sterilizer, water net | 63 Comments

Understanding the Biological Cycle of Your Koi Pond

The biological cycle is really better defined as the “nitrogen cycle” because primarily what pond keepers are concerned with is nitrogenous waste.  When it comes to elements, nitrogen is pretty common. In fact, it makes up almost 80% of our atmosphere so it’s not surprising that it should be found in many plants and animals, too. Nitrogen can be found in proteins and DNA as well as fish waste. The nitrogen cycle in your pond really has to do with what happens to the nitrogen in fish waste, decaying plant matter and uneaten food. The following is a step-by-step explanation of that process.

Koi Pond Waste Processing

1. In your pond fish excrete waste and maybe your koi munch the stalk off a submerged plant so it lies decaying on the bottom and there happens to be some uneaten food mixed in with everything else. These are not your only source of nitrogenous waste but they probably make up a large proportion of it. The first nitrogen-based chemical that will appear in your pond is ammonia. This comes about because bacteria and some fungi will subsequently assimilate or break down the aforementioned “stuff” lying on the bottom of your pond -the by-product of which is ammonia. On the scale of harmful chemicals to your koi ammonia is number one.

2. In a koi pond with a good biological filtration system there will be nitrosomonas bacteria and these guys will take ammonia and oxygen and use it as fuel and turn it into a waste product called nitrite. On the scale of harmful chemicals to your koi nitrite comes in at number 2.

3. The next helpful bacteria in the cycle are called nitrobacter. These bacteria convert nitrites and oxygen into a waste product called nitrate.
4. The nitrates are then assimilated by another suite of bacteria that do not use oxygen, these are called “anaerobic bacteria”. They live in oxygen free parts of the pond and produce free nitrogen from nitrates.

Nitrogen Cycle koi pond

Basic Nitrogen Cycle of a Koi Pond

Filter systems were discussed here but where do aquatic plants come into play? Plants, like submerged vegetation and surface vegetation (lilies), are critical parts of your pond’s ecosystem for their abilities to “suck up” nitrates, produce dissolved oxygen and block the sunlight that would otherwise help algae grow. So what is so bad about algae? Algae is good on one hand because it produces dissolved oxygen which enters the water but algae also grow rapidly then die and once that happens you will end up with a lot of decaying algae in your pond. All the dead algae will drive up ammonia levels and lower oxygen levels. Remember those nitrosomonas bacteria that use oxygen and ammonia to produce nitrites? The more decaying material, the more oxygen will be used up by bacteria leaving your pond with decreasing levels of dissolved oxygen.

If you would like to know more about water chemistry and how it affects your koi please see my article here.

Posted in Pond Care | Tagged ammonia, biolgical cycle, fish waste, free nitrogen, nitrate, nitrite, nitrogen cycle | 4 Comments

I’ve got koi fry –now what!? A step wise approach to raising baby koi

got koi fry

If you just noticed that your pond now has a million little koi fry swimming around then skip down to the feeding section but if you haven’t bred koi yet and need an introduction then read on. Spawning typically occurs in the early summer months and is very water temperature dependent – 68 degrees F is the minimum for spawning .  Your adult koi will have to be sexually mature to engage in successful mating and this typically occurs at age 2 for males and at age 3 for females.  Keep in mind when you are selecting the parents that the larger the female, the more eggs she can produce.  If you are wondering about how to tell the sex of your koi, there are different approaches to this such as looking at pectoral fin shape and size but the tried and true method is to inspect the underside of your koi.  If there is one vent (slit) then you have a male, if you have two vents (slits) then you have a female.  Usually spawning activity, and the behaviors associated with it, will take place in the early morning and may only last 30 minutes.  The whole process is a bit rough as the male needs to physically stimulate the eggs to be released by nudging the female’s belly.  After eggs are released, the male fertilizes them by releasing sperm.

Breeding Material

If you plan on having a dedicated spawning tank you will most certainly want breeding material.  This is simply material that offers surface area for the eggs to stick to.  This could take the shape of aquatic plants, ropes, a “spawning brush” or a “spawning mop”.  Most importantly it needs to be something that won’t be toxic in any way and has lots of surface area for eggs to attach.  You will want to have plenty of breeding material for the eggs to attach to-maybe around 50 to 60 percent of the bottom of the spawning tank should be covered.  The size of your spawning tank will depend on how many fish you plan on trying to get to reproduce.  It should be something on the order of 1 to 2 feet deep and maybe 6 feet by 6 feet –some hobbyists have used inflatable kiddie pools with success. After eggs have been laid and adults removed from spawning tank you should see hatching around 4 days later.  When you are satisfied with the density of hatched fish you can remove the breeding material.  So what will the eggs look like? See below.

example of koi eggs

Thanks to Anthony R. for submitting these pis of his koi’s eggs

Tank/Pond Conditions

You may choose not to go with a separate fry tank or pond and simply let it happen in the main pond.  If this is the case be aware that if you have goldfish amongst your adult koi you will have some egg loss due to the goldfish’s appetite for koi eggs.  Your koi eggs will hatch around 4 days after they are fertilized.  They will then attach themselves to structure like the side of the tank or pond for 2-3 days where they will be feeding off their yolk sac. If you are seeing a great deal of swimming koi fry and also a lot of eggs at the bottom feel free to remove those as they most likely failed to fertilize and will only drive ammonia levels up.  Be sure to monitor all your water chemistry, especially ammonia and pH.

What to feed your koi fry?

At around the 10th day (sooner depending on water temp) you will notice your koi fry trying out their new-found ability to swim and it’s at that time that feeding should begin.  A lot of koi enthusiasts will start off with something called “infusoria” which is not a thing but more of a size classification.  Generally, it’s defined as very small aquatic organisms and for koi fry those should be live daphnia (water fleas) and/or brine shrimp (“sea monkies”).  If you can’t obtain infusoria you can try chicken eggs. Boil the eggs (some just use the yolks) and, in a blender, mix with about 30 or so ounces of water from the tank or pond.  Simply squirt that mixture over the surface of your breeding tank or pond.  You will want to feed around 4 times per day.  In general you are trying to match the size of the food with the koi fry such that it is an appropriate size for them to eat. After about a week of this mixture you can switch to a powder called “fry powder” which can be sprinkled over the water’s surface.  You can also use standard protein infused koi pellets and basically grind them up into a fine powder and select for a certain grain size by shaking it through a sieve.  It may take a few days for the fry to associate the new powder with food and acquire a taste for it. Be sure to clean the bottom of the tank for any waste and excess/uneaten food –you really want to avoid ammonia build up. Make sure that you provide plenty of aeration for your koi fry and this is especially true in the summer when warmer water temps mean less oxygen carrying capacity of water. Some other foods that you can feed are frozen brine shrimp, growing live brine shimp in your containment tank or main pond and freeze-dried krill. You may also add, as a nutritional supplement, spirulina powder and wheat germ.

brine shrimp (sea monkey)

Daphnia water flea copy


One mistake people make is trying to keep all the koi fry, that’s a bad idea. You definitely want to “thin out the herd” because by doing so you create a more healthy environment for the remaining koi. Your first round of culling should take place at around 1 inch or 25mm. This should fall at about 4 weeks (possibly longer) after swimming is first observed. Another culling should take place a month after the first or about when they are about 2.5 inches or 6.25cm. The first and second culling should remove about 80% of the initial population. Additionally, a third culling should start a month after the second one and remove 50 to 60% of what’s left (see the “Breeding Timeline” below). When culling you should be looking for deformities, undesirable coloration, erratic swimming, sluggish swimmers and generally undesirable traits. You don’t necessarily have to euthanize these fish-give some to your friends!

Final thoughts

When your koi do finally make it to a larger size and you want to introduce them to the main pond be aware that adult koi will eat most anything and the baby koi might be on the menu if they are small enough. Be sure to release them only when they are big enough that they won’t actually fit in the adults mouths!

Typical Timeline for Koi Fry

Typical Timeline for Koi Fry

Posted in Breeding Koi | Tagged baby koi, breeding koi, koi fry | 40 Comments

What are the ideal water conditions for healthy koi?

There will certainly be a lot of differing opinions on the best water conditions for koi but one thing remains constant: poor water quality leads to a host of other health problems that are certainly avoidable with proper care.  Because stress originates from poor water quality, follow these guidelines for healthy water and healthy koi.

Dissolved Oxygen

Oxygen levels should be at a minimum of 5.0 mg/L for koi.  In the fish world, there is some variation with the tolerable level of dissolved oxygen in the water but 5.0 is a good baseline.  As a reference, 5.0 mg/L is the minimum for koi and 18 mg/L is the physical maximum that water can hold.  Just as a reminder though, cold water can hold more dissolved oxygen than warmer water so higher summer temperatures (and overcrowded ponds) will lead to lower dissolved oxygen, which is really when you will want to pay attention to it the most.  Oxygen becomes dissolved into your koi pond in several ways.  At the very surface there is limited diffusion occurring between the atmosphere and the water and that accounts for only a small amount of dissolved oxygen.  Turbulence will also agitate the water enough to generate dissolved oxygen in your pond and this often comes in the form of falling water as from a small water fall.  A tried and true and popular way to increase the dissolved oxygen in a koi pond is by an air stone on the bottom of the pond or by spout or fountain shooting water up into the air.


Okay, back to chemistry class everyone because its time to discuss pH.  As you may recall pH has something to do with acids.  Its all about acidity and alkalinity.  The pH scale is a logarithmic one meaning when your pond jumps from 7 (neutral) to 6, its not simply getting a little bit more acidic, its getting 10 times more acidic.  Conversely, when your pond tests at 7.5 and then gets increasingly alkaline by jumping to 9.5,  then your pond just got 100 times more alkaline (10 times 10).  So it’s a big deal when your pH changes and can definitely affect your koi in negative ways.  pH, or power of Hydrogen, should range in your pond somewhere between 6.8 and 8.2 but do your best to keep it as stable as possible.  If you were to test your pond multiple times a day you should notice a daily fluctuation in pH.  So what’s going on?  As part of the natural process of photosynthesis and respiration of aquatic plants and algae they use up dissolved carbon dioxide (that’s a good thing) but, at night, they release it as well (not good).  The common denominator here is carbon dioxide because of its power to increase the acidity of the water.  Of course, your fish are respiring as well which also adds to the carbon dioxide load in your pond.  A good way to add a long-term pH buffer to your pond and protect your fish from pH swings is to add some calcium carbonate material to your pond. This comes in gravel form or rocks and may be sold under the name “agricultural limestone”.  PH buffering capacity (better described as “KH”) is also why its nice to have concrete-lined ponds -the concrete tends to buffer against pH swings.


No discussion of pH is complete without also talking about KH (or carbonate hardness or alkalinity).  Your pond’s KH level will affect how susceptible your pond is to pH fluctuations.  If, for example, your KH reading is particularly low then anything you do to get your pH back to an acceptable range may be short lived as your pond lacks the ability to buffer future pH swings.   KH should be around 105 ppm with a possible deviation of plus or minus 15 ppm (up or down from 105).  Baking soda (sodium bicarbonate or bicarbonate of soda) will increase your pH making it more basic. Conversely, you can add white vinegar to lower, or make more acidic, your pond water.

GH (General Hardness)

GH is really a measurement of the total quantity of dissolved minerals in your water.  Typically, magnesium and calcium are the primary minerals referred to when discussing this parameter. Of all the water parameters to test GH may be the least critical but a good range to shoot for is 60 to 160 ppm though some pond owners will have higher GH readings than that with no issues seen in their fish.

Ammonia, Nitrites, Nitrates

As you may recall, the general cycle of waste in your pond starts with ammonia excreted by your fish then bacteria and oxygen break it down to nitrites which later get broken into nitrates then free nitrogen.  Ammonia, nitrites and nitrates all have the ability to cause health problems for your koi if their levels are not kept in check.  Along with other health problems, ammonia can essentially burn your fish’s gills and reduce its ability to extract dissolved oxygen from the water.  High nitrites can damage your koi’s kidneys and nervous system and high nitrates, for extended periods, can cause your fish’s immune system to be compromised.  Ammonia and nitrites and the most troublesome when it comes to health problems for your koi but don’t underestimate the power of nitrates over long periods of time.  Here is a guideline for these three water chemistry measurements.


ammonia: levels should be zero. Depending on your pH, you can get away with 0.5ppm (parts per million) or 1 ppm for a short period of time but keep in mind that above a pH of 8.0 ammonia becomes more toxic.


nitrites should be less than 0.25 ppm but ideally you should have a reading of zero.


nitrates: a reading of 20 to 60 ppm is acceptable.



The use of salt in koi ponds has, for long time, been a tried and true method to deal with various water quality and health problems that arise.  Some of the benefits of salt is that its a cheap way to keep some disease at bay, control algae and may also lower nitrite toxicity. Additionally, salt plays a part in the osmotic pressure between the fish and the outside aquatic environment.  There is a differential between the solute concentration of the fish’s blood and the fresh water that it swims in so the addition of salt actually lowers that concentration differential and makes it easier on the fish by reducing the amount of work its body has to do.  A salinity of up to 5 ppt (parts per thousand) or 0.5 % is acceptable.  Testing your pond’s salinity is commonly done with a simple tool called a refractometer.


Temperature obviously plays a big role in the overall health of your pond and  it warrants your attention.  Temperature can exacerbate existing problems, especially higher temperatures.  For example, warmer water holds less dissolved oxygen and ammonia can be more toxic.   Although koi can handle temperatures of between 35 and 85 F degrees its best to keep your fish in water that ranges between 65 and 75 F degrees.  And as with pH, try to avoid large temperature swings.

Posted in Pond Care | Tagged ammonia, dissolved oxygen, health, KH, koi, nitrates, nitrites, pH, salt, water chemistry, water temperature | 40 Comments

The Major Koi Varieties and Their Traits

Presented here are what many consider the 13 major varieties of koi or “Nishikigoi”.  There are certainly some koi practitioners that may consider there to be up to 16 varieties (and even up to 22 if one counts newer strains of koi).  This summary includes some history of the variety (where applicable) as well as physical descriptions of each variety.

1) Asagi and Shusui

These two varieties are typically clumped together.  “Asagi” means light blue.  These koi colorations follow a net-like pattern where their backs are predominantly blue or gray and their bellies are red or orange.  As these varieties grow older and large they tend to develop black spots in the head area.



2) Bekko 

This variety was actually developed back in the early 1800’s and is recognized by their tortoise shell like pattern.  Some of the more common colors can be orange, red, yellow, or white with black undertones. This variety tend to have a solid base color (such as orange, red, yellow or white) with black markings typically occurring above the lateral line.  Bekko can be more desirable to a breeder if the specimen has no markings on the head region but in general they aren’t usually a variety that one sees winning big competitions.



3) Hikarimoyo Mono 

Hikarimoyo translates into “metallic pattern”.  The colors on these koi will be very pronounced-these are very vibrant looking fish with a distinctive metallic look.



4) Hikari Utsuri Mono 

This variety of koi are bi-color and have unmistakable metallic scales.  They are similar in appearance to fish of the Utsuri lineage but have a shiny look.

Hikari Utsuri Mono

Hikari Utsuri Mono

5) Kawari Mono 

Koi taking on this moniker often don’t readily fit into any other category very easily.  This newer variety is will include koi such as karasu goi, goshiki, and ki goi.  This variety is not all that common, especially those specimen that are large in size.


Kawari Mono

Kawari Mono


6) Kinginrin 

Two things are distinctive about this group: 1) they have a bright metallic sheen and 2) they tend to have a silver coloration that typically occurs in a variable distribution on the body.  Metallic scales were first seen in 1929 and the name translates into “gold and silver scales”.  These specimens will almost always look more radiant in sunlight.  The most valuable kinginrin are those that have a unique pattern covering the region between the “shoulder” and back.



7) Kohaku 

Definitely the most popular of all the varieties, kohaku is arguably one of the most valuable as well.  The first “official” modern Kohaku was most likely spawned sometime around 1888 in Japan.  It is said that koi hobbyists may experiment with rearing other varieties but ultimately everyone always comes back to Kohaku.   There are numerous types of koi that occur within this variety but they distinguished by radiant red markings on a solid white body.  Additionally, this variety will have a red pattern on its head as well.






8) Koromo 

Not quite as common as some of the other varieties these koi have a blue or silver undertone with red and white markings over it which gives the fish the appearance that they are wearing a “robe” (which is what “koromo” translates to).  Those specimen retaining blue crescent markings in a predictable pattern can be very valuable to a breeder or buyer.  Those fish that have heavy markings of red or white tend to not be as valuable as others that have an equal amount of each color.  Additionally, those specimen that lack head markings also tend to be of greater value.



9)  Ogon 

When thinking of this popular variety think about gold because these koi will have a metallic gold appearance that can vary from light gold to a darker gold.



10) Showa Sanke 

Developed in the 1920’s the Showa are named after the Emperor of Japan at the time. This variety is most commonly referred to as just Showa and is predominantly black with some white and red markings on the body.  The black coloration typically goes all the way to the belly with the head and pectoral fins also taking on the black coloration.


Showa Sanke

Showa Sanke

11) Taisho Sanke 

Developed around 1917 in Japan, this koi variety translates into “tricolor” due to its primarily white undertone accompanied by red and black markings.  The black markings (sumi) are typically confined to the area of the body above the lateral line.  When the fish is young the black markings are not as defined but as it ages and grows the markings take on the more desirable sharp edged sumi.

taisho sanke

taisho sanke

12) Utsuri Mono 

Developed in the late 1800’s this koi variety is typified by a black undertone accented by yellow, white or red markings.  One thing that distinguishes this variety is their pectoral fins; they are black and have a triangular shape.


Utsuri Mono

Utsuri Mono


13) Tancho 

Perhaps the easiest to identify the tancho koi is snow white with a red marking on the top of the head, usually a circle.   This is a highly prized variety especially if they have no additional markings except a near perfect red dot on the head.  This red marking should not extend to the nose or as far back as the shoulder.



If the diversity of these varieties interest you enough to breed them, please click here for more information on koi breeding.

Posted in General Koi Information | Tagged kohaku, koi, ogon, showa, tancho, variety | 11 Comments