“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 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 that essentially tint your water a certain color and reduce the available light in your pond.

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.

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.  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 Pond Care | 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 | 45 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.

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 | 2 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.

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 Koi Care Information | Tagged baby koi, breeding koi, koi fry | 26 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.


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.

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.


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 | 34 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 | 9 Comments

Aquatic Plants for Your Koi Pond: Why They’re Important and How to Choose the Right Ones

Adding plant life to a koi pond helps improve pond life for koi, as well as adding beauty to the pond itself.

Koi owners need to make sure they select the right aquatic plants that will harmoniously co-exist with their koi. They also need to ensure that their plant placement is done properly as well as not planting vegetation that will just be eaten by the koi!

 The benefits of including aquatic plants in a koi pond

Aquatic plants are considered an excellent addition to any koi pond. Aquatic plants, in fact, help increase oxygen production in the water, helping to keep the pond properly aerated for koi. Their presence also helps keep the water cool by providing shade to the koi. Additionally, around the spring breeding season submerged plants act as a critical surface onto which female koi attach their fertilized eggs.


The presence of plants also prevents the spread of algae from getting out of control. The shade plants provide reduces incoming light into the pond and therefore limits photosynthesis of algae. Their natural ‘filtration’ system prevents blanket weeds (string algae) from forming, mainly through absorbing harmful nitrates that lead to their formation in the first place.

 Tips for introducing koi to plant life

The best way to introduce plants into a koi pond is building a plant shelf. This shelf can be built along the edge of the pond itself. It’s a container where water plants are suitable for planting. It’s a good idea to weigh down the plants with large rocks or stone to form a barrier between the base of the  plants and koi, preventing the risk of the koi eating the plants. Pond owners should be aware that predators like raccoons may use the shelves as a tool for feeding on your koi. For more on how to prevent pond predation see this article.


A vegetative filter may be an alternative to introducing aquatic plants to your pond. In this system the plants are grown in a separate containment area that connects to the main pond. The plants here can serve as a natural filtration system as water from the main pond travels in and out of the contained area. This gives you all the filtration benefits of having aquatic plants without the risk of your pond plants being eaten or dislodged.


Of course, you can always place aquatic plants directly into the pond itself. There are several options to choose from when deciding on which aquatic plants to put in your pond.   Pond plants can be divided into 3 main categories that are discussed below:

1)      Floating plants

2)      Shallow-water marsh plants

3)      Submerged plants


1)      Floating Plants

This type of pond plant can be truly free floating with its main vegetation on the surface while the roots hang down, unattached or there are types where the roots are attached to the muddy bottom. The benefits are that they are easy to care for, they provide plenty of shade for koi and they compete with algae for nutrients as well as blocking light that would have otherwise helped algae to grow, all of which greatly reduces algal growth.  Additionally, they remove a lot of the existing nitrogen and phosphates in the water and thereby do a great job of filtering the water. 


Water Hyacinth

Some popular choices for floating plants are water hyacinth.  This species is an annual in the colder regions of North America but a perennial in the warmer parts of the States.  They bear purple or blue flowers and their roots form a compact “nest” beneath them.  These plants do a great job of filtering the water of excess nutrients. 

water hyacinth in koi pond

Water Hyacinth

Water Lettuce

Another free floating plant is water lettuce.  This is more of a tropics/warm climate plant and forms compact leaf clusters on the surface with a compact root mass forming beneath the plant.


Water Lettuce in a koi pond

Water Lettuce


Water Lilies

When it comes to floating plants with attached roots water lilies are definitely the most popular choice amongst koi pond owners and may be the top choice of any of the aquatic plants.  These plants will do well in just about any region of North America in any season and can be potted and placed at the bottom of the pond.  On the surface, pond owners with water lilies will find a pleasant array of leafy covering and beautiful flowers that will nicely accent any pond.


Water lily in a koi pond

Water Lily



Looking similar to water lilies the lotus is one of the oldest cultivated aquatic plants and make a great addition to any koi pond.  Their leaves are typically very large, as much as 18 inches across which is great for providing shade to your koi in the summer.  Often confused with water lilies the lotus flower is very beautiful and also fragrant.  A word of caution should be noted here as these plants have a substantial growth rate and are best planted in larger koi ponds. 


Lotus in koi pond



Water Poppy

Water poppies produce small oval leaves and yellow flowers and are a great choice for koi ponds.  They grow fairly quickly in summer and add a nice touch of yellow to your pond while filtering the water.


water poppy in a koi pond

Water Poppy


2)      Shallow Water Marsh Plants

These type of aquatic plants are typically planted on the edge of your koi pond in the shallows.  They are usually very lush and do best in only several inches of water.


Umbrella Plants

These tropical region aquatic plants do well in shallow water and for those living in colder climates they need to be brought in during winter.  Umbrella plants, as the name suggests, have umbrella-shaped leaves at the end of long stalks.


umbrella plant in a koi pond

Umbrella Plant


Water Iris

A favorite amongst koi pond owners the water iris comes in several different species.  They have long, sharp leaves and depending on the species may produce flowers in colors ranging from blue, white or yellow.  These plants are typically planted in pots that are then submerged.  Most iris will do great both in full sun or partial shade which is nice for those with a lot of tree cover nearby.

water iris in a koi pond

Water Iris


This plant produces a slender green stem and is fast growing.  It is best placed on the peripheral parts of your pond and will do great in partial shade.


horsetail in a koi pond



3)      Submerged Plants


Suberged plants are usually grown in pots then placed at the bottom of a koi pond.  Referred to as oxygenating plants this class of aquatic plants do a great job of removing excess nutrients from the water such as nitrites as well as CO2 and add oxygen to the water.  One word of caution though, these plants are often uprooted and eaten by grazing koi so care must be taken to protect them.



This submerged plant is a fast growing oxygenator and requires a good deal of light. These plants can grow up to an inch per day and can be propagated using cuttings.


fanwort in a koi pond



American Waterweed (Elodea)

These plants do well with pond substrates that are silty.  They are completely submerged with the exception of small white flowers that bloom at the surface.  It is great at utilizing the dissolved CO2 in the water and providing cover for fish, especially small koi.  Sometimes the leafy stalks will break off and float away to take root in another part of the pond.  They do very well in milder climates.


elodea in a koi pond



Water Purslane (Ludwigia)

There are many species in the Ludwigia family but Red Ludwigia is a good choice for your pond as this plant grows fast and is a great oxygenator.  It can be planted as a submerged addition to your pond or you can let it float.  They produce small flowers and their leaves are a reddish or purple color.  They typically do well in a lot of direct light.

water purslane in a koi pond

Water Purslane

Posted in Aquatic Plants | Tagged aquatics plants, koi eggs, koi ponds, oxygenators, shade plants, water filtration, water quality | 17 Comments

Top 5 Most Common Koi Pond Problems and Their Solutions

Typical koi pond

Having a Koi pond can not only increase the visual appeal of a property, but it can also aid in developing a passion for an environment that you are able to maintain for yourself.  Koi ponds can certainly encounter a number of issues throughout time, especially considering the amount of time and effort that one puts into maintenance, but this does not mean that such problems cannot be solved and alleviated with a few simple suggestions.  The following will outline 5 of the most common problems associated with Koi ponds, as well as ways in which such problems can be solved.

  1.  Predation is a serious issue with Koi ponds, especially during the overnight hours.  Cats, raccoons, and even larger coyotes have been known to prey on the fish in Koi ponds.  If you are finding this to be an issue for you and your fish friends, then consider making the water too deep for large birds or animals to stand in  or place netting on the surface of the water to pose as a barrier between the fish and the predator.
  2. Parasitic infestations of your fish can not only be difficult to identify, but they can be nearly impossible to identify as many are too small for them to be seen by the naked eye.  If you are experiencing an issue of this nature, then consider a better filtration system such as one that incorporates a UV sterilizer. For more on koi diseases see this article.
  3. If you find that your Koi pond has excessive algal growth which can decrease your ability to see your fish, then there are several ways to manage the algae in your pond.  You can choose to either tint the pond water, which will reduce the ability of the algae to gather sunlight, or you can add just a slight amount of salt in the pond, but only if you do not have other plants growing that don’t have some salt tolerance.
  4. Low oxygen levels can certainly be one of the leading causes of the death of Koi fish.  Unfortunately, many people do not realize that they are having this issue until it is too late.  Adding plants, air stones or a small fountain or waterfall to your pond should create sufficient oxygen and flow to keep your fish alive and happy.
  5. High pH levels and high bacteria levels can all contribute to the death of fish.  Koi ponds may have a pH range between 6.8 to 8.2 but 7.0 to 7.5 is really ideal.  There will most likely be natural daily swings of pH of a small amount but that is not something to be concerned about as long as they are small.  The concern becomes big swings in a short time or generally pH levels that are outside the acceptable range causing koi skin to become vulnerable to bacterial infection.  Two main solutions to keeping pH levels in check are regular testing and if need be adjustments via buffers and acids.  In short, buffers will increase pH while the addition of acids will reduce pH.
Posted in Koi Care Information | Tagged algae growth, dissolved oxygen, koi problems and solutions, parasites, predation, water chemistry | 54 Comments