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 | 31 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. Water Quality

This is THE leading cause of the death of Koi fish.  It largely stems from the fish’s waste products and the first iteration of that is ammonia. Unfortunately, many people do not realize that they are having this issue until the koi’s gills are burned by the ammonia.  

You can use chemicals in the short term that sequester the ammonia but ultimately you really want to address your filtration and levels of beneficial bacteria.

In the biological cycle of a koi pond ammonia is produced from fish waste, which gets turned into nitrites, then nitrates.  Its important to become familiar with the basics of this process to understand better how to treat and prevent water quality issues.  This article and graphic describe this process in more detail. 

Really high or low pH’s can also 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.

2. Diseases

Parasites on or in 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.  

Bacteria are everywhere in nature, including your koi pond.  There are good bacteria and not-so-good bacteria.  If your fish are stressed for any reason that can increase their vulnerability to bacterial infections (especially if they have a lesion or injury).

Water quality is at the heart of disease prevention so although you can treat diseases as they arise you will be doing yourself and your fish a favor by getting your water chemistry right.  

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. Algae Growth

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.  

At the heart of algae problems is water quality/chemistry.  If you can remove one or more of the elements that allow algae to thrive you will come out on top.  

Algae Box-what algae needs to grow

4. Overcrowding

When it comes to koi, less is more.  You don’t necessarily get more satisfaction out of 30 fish than you would with 10.  Keeping your population to a manageable level avoids lots of other potential problems like excessive waste build-up, depletion of dissolved oxygen, stress from crowded conditions leading to disease.

The more koi you have, the more koi you will have.  Koi breeding will really inflate your population size.  Crowded conditions will cause a physiological response in koi that “tells” their bodies to reduce growth  hormones resulting in smaller koi overall.

5. Predation

It can be a serious issue with koi ponds, especially during the overnight hours.  Cats, raccoons, wading birds, river otters 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.

In conclusion, taking care of your koi and the pond they live in is a process but one that you can learn and get better at over time.  Its easy to get overwhelmed by what may appear to be complex but any large problem is merely many small problems that can be tackled one by one.  By addressing water quality first and spending the most time on mastering that, fish health and pond health will follow.

Posted in Koi Care Information | Tagged algae growth, dissolved oxygen, high ammonia, koi problems and solutions, parasites, predation, water chemistry | 77 Comments

Selecting Food for Your Koi

feeding koi

Koi are omnivores, which means that they consume both plant and animal matter. In fact, they often prefer eating aquatic larvae and insects. Koi fish make incredibly beautiful pets—though they’re also incredibly voracious fish. These elegantly decorated fish actually devour nearly anything that finds its way into their water. Since koi fish eat practically anything, you have to make sure your fish gets fed a diet that’s both nutritious and balanced.


There are many options for koi food. These options oft include live insects, commercialized dry foods and supplements, fresh foods and even occasional treats. The most common foods available for koi fish are commercialized foods, often comprised of specially formulated pellets, granules, chunks, flakes and tablets. Commercial koi foods can be easily stored and are rather inexpensive—not to mention, they also contain a sufficient amount of nutrient fortified ingredients.

 Important Factors when Choosing the Right Food

When you shop for koi food, you need to consider two factors. The first factor involves the age and size of your pet, while the second often involves the time of year. It’s recommended to feed your koi more protein in the summer than during winter months, when they are less active. Smaller-sized food like small pellets are more ideal for smaller koi, while bigger koi naturally feed on larger-sized foods.

 Koi Food Supplements

Supplements for koi help enhance the overall health of your pet. They also provide beneficial effects that support and boost their immune systems. In fact, many types of commercial koi food include some form of nutrition supplementation. There’s also supplement powders made to be mixed into koi foods.


Koi fish can also consume fresh foods, however it’s best to sparingly give your fish these foods. A number of fruits and vegetables can be used as koi food, including lettuce, oranges and garlic. Insects and other aquatic critters are also ideal koi ‘treats’ to supplement their diets.


Many of these insects and critters range from prawns, soft-shelled crickets and worms like waxworms and bloodworms. These critters provide a protein boost to their diets. It’s recommended, though, to provide your koi fish with pesticide-free critters, as the chemicals may likely cause a detrimental effect to their well-being.


To ensure that your koi gets the best food possible, don’t forget to review the labels on the food you’re offering your koi. If you’re purchasing their food online, make sure the retailer has a sufficient amount of information about the food you’re buying for your pet. If you can’t find any information about a particular product, it’s advised to avoid purchasing it.

Posted in Food and Nutrition | Tagged aquatic larvae, bloodworms, dry food, koi food, live insects, proper nutrition, selecting food, waxworms | 2 Comments

How to Breed Koi for Profit

It’s not as out of reach as you might think to breed Koi fish for profit, as thousands around the world have done with great success. Knowing how to do it, though, is another matter altogether; let’s review exactly what you need to do in order to breed Koi fish for profit and turn a very unique source of income into a business and a successful and profitable endeavor.


What’s Your Breeding Stock Like?

First and foremost, it’s critical that you have a good Koi breeding stock to source from and begin breeding on your own, or else your job may be over before it begins. A good stock means working with a good supply of quality fish, and you may need to spend some money to ensure biological and genetic diversity as you get started breeding Koi.  A reasonable amount to spend on parents is around $1000 or more for a quality breeding pair of something like Kohaku.  You’ll want to make sure that they are at least 3 years old as that is when they begin to be sexually mature.  The value of your offspring will be largely dependent on the value of your parents, so choose wisely!


Get Your Breeding Ponds In Order

The next most important aspect of breeding Koi fish is having a high quality space for them to live and grow. Breeding ponds don’t have to be expensive, but you must ensure that they are safe and secure from predators and adequately cared for.  In addition, it’s critical that you use specialized filtration equipment to generate clean water levels that are healthy and sustainable.  Be prepared to spend some up-front capital on setting up your koi systems.  You will need space and resource to handle all the offspring produced.  Plan on devoting at least a couple hours a day to general feeding and maintenance.  You can easily spend several thousand dollars on the initial investment of tanks, filters, medications, food, chemicals, water etc. so keep that in mind as you financially plan for breeding.


Don’t forget proper nutrition!

When you finally spawn your first generation of newly-bred Koi fish, congratulations – now the fun part starts! You must feed them hatched brine shrimp and crushed Koi pellets to ensure that their skin and scales are bright, and that they are healthy and vibrant. Feeding isn’t cheap, but it will help you reach the culling process, which can be one of the most difficult parts of breeding koi.


Culling takes the right mindset

When it comes to culling Koi, you can’t have a queasy stomach about it.  Your koi parents will produce of 500,000 eggs at a time though not all will make it to the juvenile stage you can be certain that you will find yourself overwhelmed with little koi unless you have the space for them!  Koi are the gift that keeps on giving! Certain fish won’t look great and won’t be good to sell to breeders or homeowners and just need to be removed to ensure you maintain the genetic stock. Because of that, it’s important to cull out the ones you need to remove, and do it humanely and quickly.


Selling: The Endgame

For most breeders, selling Koi initially isn’t the easiest thing to do, as it takes time to build up a reputation and prove that you produce quality fish. But rest assured that with hard work and a transparent process that shows buyers what you have been able to accomplish, you can, over time, breed Koi successfully and make it so that they turn a profit with their breeding and more.  So what can you make selling koi?  Some companies produce and sell 20,000 to 30,000 fish a year with prices ranging from $15 to $5000 each -these kinds of companies may do $500,000 a year before expenses.  In fact, when it comes to value koi can command some seriously large amounts of cash!  One particular Showa specimen went for over $147,000.  Oftentimes highly prized koi act as a status symbol for those wealthy enough to afford them.  Similar to owning a rare historical artifact, these prized competition fish are a source of national pride for wealthy Asians as Asia is where koi breeding first started.  Just as in horse racing, these fish are often bred by world renowned breeders for the explicit purpose of breeding a champion.  


Probably the four most common varieties that one will see in  a koi competition are Showa, Sanke, Kohaku and Shusui.  For the breeder at home interested in getting into breeding for profit these are 4 good varieties to start with.  

To be sure, if you do it right and have quality fish you can easily get 10X the value out of your investment from  breeding koi.  The other good news besides all the eggs koi constantly produce is that they live a long time.  A life span of 50 years is not unheard of and there are even stories of koi living to well over 100!  

When it comes time to sell some or all of your koi the best way to sell them is to make sure you have some good, clear photos of them.  Preferably put the koi in a royal blue container, with no glare, reflection or ripples in the water. Be sure to get the whole fish in the frame from straight above, not an angle shot. You may have to take a dozen or so photos to get one usable image. Then post those photos on whatever site or sites you would like to sell them on.   Be patient, and be ready to invest some money to get started, but it is possible to breed Koi in this manner and make a profit!


Posted in Breeding Koi | Tagged breeding stock, culling, nutrition, pond maintenance, selling koi | 63 Comments

Koi Diseases and Their Treatments

koi diseases



For a koi, life can be full of peril. The fish in an outdoor pond are subject to not only birds of prey and raccoon but to things you often can’t see that live in your water and infect your fish. Fortunately, there is a great deal of information on koi diseases and an equal amount of treatments but the most important thing is being informed on those diseases. The more you know about koi maladies the better you can treat them. Listed below are most of the more common koi diseases and some of their treatments.


One of the most common diseases found in Koi is Ich (aka; White Spot disease). It is a protozoan that begins its growth in the pond and later attaches to the gills of the Koi as it matures. The ich parasite initially appears like little white grains of salt on your Koi. Ich can kill smaller Koi, especially in crowded ponds and can cause other bacterial infections in your fish.  It is usually borne out of poor water quality so to deal with the disease at its root, proper water chemistry will have to be achieved.

Tropical fish specialists frequently deal with Ich. It can, however, also infect cold water fish. They must attach to the fish within 48 hours of hatching or they will die. Once they attach themselves to fish, they dig into the skin and feed on the fish’s tissue. After feeding on the fish for approximately three weeks, they detach themselves and move to the bottom of the pond to reproduce. The Ich hatch out of cysts at the bottom of the pond and use small hair-like tentacles called cilia to swim about.

Treating Ich

There are a couple of widely used methods to treat ich. The first one requires the koi owner to increase the salt concentration of the pond or quarantine tank to about 0.5% over a period of days. At the same time increase the temperature of the water gradually to the mid 80’s F while increasing aeration.  This quarantine should last 2 weeks and is an effective and cheaper way to deal with the ich protozoan. The second method is a tried and true method for dealing with parasites in general and involves malachite green and formalin. Using both simultaneously is definitely going to be effective against ich but you may be able to simply treat with malachite green alone. For short treatments in quarantine, one could do a quantity of 1.5 mg of malachite green for every liter of water for up to 1 hour (or 6mg of malachite green for every gallon of water). Always wear gloves when handling both malachite green and formalin.

Dropsy (Pinecone Disease)

Fish that have dropsy often show signs of swelling or lifting of the scales. Their eyes will frequently bulge. If you ever notice this, don’t hesitate to separate the infected fish from the others. Paying careful attention to your fish in order to notice these symptoms as early as possible means that your other fish stand a better chance of surviving.

Treating Dropsy

Dropsy is, more or less, terminal. By the time you see your fish bloated with standing scales it means that there is kidney and liver failure.  Prevention of infection to your other fish is recommended with MedFinn or Debride RX. 

Tail Rot

Tail rot and fin rot are really secondary to the original problem which could be stress or poor water quality that is causing your koi to be immuno-compromised in the first place. Once they are weakened then the already-present bacteria can move in a cause physical damage to your koi’s fins.

Treating Tail Rot

One good start to treating this malady is by a 30 -50% water change of your pond. Using Mela-Fix is also a great option for dealing with the bacteria themselves and you can also add salt to your pond which will go to work on your bacteria and also lower stress levels for your koi. If you’d like you can also feed them MedFinn (just as with the cloudy eye treatment).

Mouth Rot

Mouth rot is a symptom of something larger and that is usually poor water quality that is causing your fish’s health to be compromised and open to infection. You’re going to want to stop feeding for the time being and start improving your water quality by doing a 30% water change. Next thing would be a light salt bath treatment and perhaps a treatment of Mela-Fix. You will also want to monitor your water quality by testing it regularly. You can also remove the fish and treat the sores with hydrogen peroxide or iodine.

Chilodonella: Some of the symptoms included with this protozoan parasite are: dying on the surface and rolling over on the fish’s s sides. This is a notorious killer of koi.

Treating Chilodonella: You will want to increase the salt concentration in the pond for 2 weeks as well as increasing aeration.

Aeromonas Bacteria: These bacteria are associated with ulcers and fin erosion.

Treating Aeromonas: The koi will need to injections of Chloramphenicol.  This treatment should yield positive results in 3-4 days.

Pseudomonas bacteria: Like its cousin, aeromonas, this bacteria is also associated with ulcers and fin erosion.

Treating Pseudomonas: Infections of this nature will require an injection of Baytril.

Columnaris: This bacteria will attack sites of injury but will cause fin, tail and mouth rot.  Additionally fish can be vulnerable to it during times of stress.  Your fish may develop a white film on their skin and display sunken in eyes.  It can be a rapid killer so be sure to take swift action.

Treating Columnaris: Feeding your koi MedFinn or Debride RX will definitely help your fish with an “inside out” treatment strategy. 

Anchor worm (Lernea)

Anchor worm, also known as Lernea is a crustacean parasite that attaches to, and digs into the skin of fish. The female Lernea attaches to fish while males do not. The worm feeds on the fish, damaging its tissue. This leads to a bacterial and/or fungal infection on the fish. Another crustacean parasite, Argulus also attaches itself to fish and causes damage to tissue.

Treating Anchor Worm: They can be removed using tweezers or other small pincers. After removal, rub some Neosporin on the infected area. Use Dimilin, Dylox or Lufenuron to treat the pond.  Though Dimilin is probably your best bet for clearing up anchor worm there are other products out there that have a good track records as well and those include ECORX and Anchors Away.

Argulus (Fish Lice)

These unwanted invaders have eight legs and rounded bodies. They also have to big suckers which are used to attach to the fish. Their appearance leads to their nickname, “fish lice”. These parasites can cause considerable irritation to fish and can lead to bacterial infections.  The irritation will lead to flashing and rubbing which should tip you off that something is wrong and the koi are trying to get some relief.

Treating Argulus:  As with anchor worm, treatment will consist of Dimilin but another product also works as well, Lufenuron.  You should see positive results in a matter of days.


Mild or moderate infections can be treated and possibly cured if they are caught early. These types of fungal infections are not typically contagious and usually only a single Koi becomes infected.  Fungal infections in fish almost always begin externally and start through a break in the outer skin layer of the fish. Affected Koi usually display fluffy or cotton-like growths on their skin. These growths may also exhibit a green tinge because of algae growth on the fungus. There may also be raised white, brown, yellow or green irregular bumps seen on the fish’s fins. Most infections can be successfully treated if caught early so it is important to visually inspect your fish frequently.

Treating Fungus: If the water temperatures are cold its most likely fungus however epistylis is also a possibility.  Fungus can be removed by gently rubbing the area with a cotton swab while the infected area must be treated with an antibiotic or antimicrobial cream immediately afterwards.  If you are not sure if its fungus or epistylis try raising the salinity of the pond or quarantine tank- fungus won’t be negatively affected by salt but epistylis will.


Your Koi fish may have Lymphocystis if its displaying any buff discoloration on its skin. Another sign of Lymphocystis is rough, raised lesions on its skin.  Though not typically contagious or fatal it is can be disfiguring to the fish carrying this virus.  This condition often occurs when the water temperature in the fish’s environment has changed. 

Treating Lymphocystis: You will want to put the infected fish in a quarantine tank and increase the heat.  There is a treatment containing “neutral acriflavine” that will help defeat the virus (this product takes the brand name “Lymphocystis Cure”).  It is entirely possible and not uncommon for the virus to go away on its own.

Epistylis is an uncommon parasitic infection that is dangerous and can cause other diseases in your Koi. It is usually caused by poor management of the water, resulting in dirty water infected with parasites. If you do not regularly change the water in the pond, it can easily become a host to these parasites. Epistylis looks like a fungus and thrives in ulcers and wounds on Koi fish. You can identify an infected fish if you see white colored tufts in and around ulcers and wounds on the fish’s skin.

Treating Epistylis: Change the water in the pond and add salt (0.3% concentration) to combat these parasites.  One can also put the affected fish in quarantine for 2 weeks while raising salt levels to 0.3%.

Its always nice to have a comprehensive reference manual you can look at when concerned about your koi’s health. My “go to” manuals are the Manual of Koi Health and Koi Health and Disease (Ed. 2). Edition 2 of “Koi Health and Disease” is supposed to be much more comprehensive than the first edition (the one I own) plus it has quick reference charts for disease diagnosis and its spiral bound for ease of use.

Fish normally eat less during the winter and by eating less, fish tend to lose a bit of weight. This normal change sometimes masks Skinny disease.

Skinny Disease

The disease is caused by a bacterial infection that causes the fish to have a sucked-in gill appearance. Its head will often appear much bigger than the rest of its body.

Treating Skinny Disease: Adding extra food to the fish’s diet can usually clear up this disease. However, sometimes this doesn’t help and if the bacterial infection persists, adding erythromycin to the fish’s food normally clears the infection up quickly.

Carp Pox

Similar in nature to Lymphocystis, carp pox is common, not very contagious, not usually fatal  but can disfigure.  Unlike its cousin, this virus causes soft and waxy looking raised growths. They are often described as being like pinkish, melted wax on the koi’s skin.

Treating Carp Pox:  There is no effective treatment for this virus but fortunately it usually goes away on its own.  Gradually heating the water may expedite the virus diminishing.  For some pond owners this is just something that shows up every winter and spring and goes away with the onset of summer.

Spring Viremia of Carp (SVC)

As the name suggests, this viral disease likes cold water and shows up in spring when the water is still cold and your koi’s immune system is not in full swing.  Some of the symptoms that you may see are a reddening of the skin and swim bladder inflammation.  It isn’t usually a primary disease as it will normally only come in after another debilitating affliction like a bacterial infection distresses the fish.  Fortunately, SVC is not usually fatal.


This disease also known as “hole in the head” disease is protozoan parasite responsible for lesions in the dermal layers of koi.  You will notice your koi being lethargic and, more definitively, you will notice an erosion of the skin (and usually the fins as well).  Your koi will isolate themselves in a given area of the pond and, as a result of the disease, will darken in color.

Treating Hexamita: As with many diseases, you will want to quarantine this fish.  You will also want to establish a treatment course with a product called Flagyl for 10-12 days.

Cotton Wool Disease

Another disease Koi sometimes suffer is called Columnaris, which is sometimes also called Cotton Wool Disease. White threads in the fish’s mouth and a dry skin appearance are the main characteristics of this disease. Sometimes the color of the Koi becomes darker and white sores can appear on its skin. It is not always easy however to determine if the fish has the fungus in its gills. However, if the Koi stays near the surface of the pond, gulping for air, it is a good indication that the fungus is, in fact, in the gills. The Koi can also develop a soggy belly and a slimy coating over its skin.

Treating Cotton Wool: You can put potassium permanganate in the water to help clear up the condition. Additionally, injecting antibiotics and treating the wound directly will help care for the disease. You should separate the infected Koi from the population and treat the water so the other fish do not become infected.


There are two main classes of flukes; 1) gill flukes and 2) skin flukes. Both kinds are microscopic so if you suspect your fish are suffering from flukes you will need a microscope to verify it. Dactylogyrus or gill flukes will attach to the gills and, as the name suggests, body flukes or gyrodactylus attach to the body. Having hitch hikers is usually not a problem…except if you’re a koi and they are parasitic! Flukes tend to eat away at the protective “slime” coating of your fish thereby exposing them to harmful bacterial infections and causing ulcers. They also are an irritant and cause your fish to itch and subsequently rub themselves on the bottom or side of the pond in an attempt to itch and rid themselves of the parasite. Gill flukes can eat away at your koi’s gills so much that the koi will not be able to assimilate oxygen from the water. If you suspect a fluke infection be sure to look out for this behavior.

Treating Flukes: You can quarantine but it is likely that your entire pond is afflicted with the flukes or their eggs so you can treat with medications like Microbe-Lift Praziquantel, potassium permanganate or Aquascape Praziquantel (both Microbe-Lift  and Aquascape have the same active ingredient; “praziquantel”).  Some additional treatments are SupaVerm (will kill goldfish but won’t affect your beneficial bacteria) and Fluke Tabs.

Oodinium Parasites:

The disease caused by these parasites is sometimes called Velvet Disease because it resembles a velvety golden dust, which covers the fish.  Other symptoms include ragged fins and a loss of scales and skin.  Though it is somewhat rare there are treatments.

Treating Oodinium:

Adding salt to the pond’s water does not normally clear up Velvet Disease. The best option is to add 37% Formalin to the water as this has been shown to be most effective.  Alternatively, Simazine can also be used to treat oodinium.


Costia, like Flukes, are a parasite. In this case it is a microscopic flagellate that can reproduce rapidly. Typically koi don’t suffer from costia unless they are already compromised in some way to begin with so it would be classified as a secondary illness.  This affliction is usually associated with spring time. Your koi will appear lethargic and will attempt to flash or rub on the sides or bottom of the pond to itch and rid themselves of the parasite. The skin will also appear whitish/grayish on the infected are of the koi’s body and potentially reddening fins. Though these parasites can affect the skin they will also infect the gills of your koi as well therefore you may see gasping at the surface.

Treating Costia: There are treatment options for costia. Malachite green and 37% formalin can be used but you will need to make sure there is no salt in the pond to start with.  If this treatment is chosen be sure to increase aeration.   As with flukes, potassium permanganate can be used to treat costia. Some practitioners will recommend a strong salt bath (up to 0.6%) while other treatments include trypaflavine which goes by the trade name Acriflavine and copper. Copper is used because most invertebrates, like costia flagellates, have copper-based hemolymph (blood) and therefore copper as a treatment in ponds is toxic to them. Acriflavine should be added to your pond at a rate of 1ml/liter and copper is most appropriate at 2 mg/liter. It is critical that you do not overdose with these two treatments.

Pop Eye

Pop eye is also called exophthalmia and is really not linked to any one illness but is more of a symptom of something more. It is a direct response to an excess of fluid or possibly gasses built up behind the eye which then cause the eye to bulge is distend. There could be several things that could cause this to happen. Sometimes this malady is caused by a bacterial infection while other times it is due to trauma from running into the side of a concrete pond.

Treating Pop Eye: The best course of action is to immediately quarantine the fish and do a light salt bath. You will also want to greatly reduce feeding and how much you give it. You will also want to do 25% water changes daily and monitor water quality on a regular basis.

Cloudy Eye

Cloudy eye is somewhat uncommon but it can occur. This malady is typically a symptom of something else going on rather than something attacking the eye specifically. Some causes are bacterial infection, a cataract or even lack of the right kinds of foods (which is why you want to diversify their diet and feed them only quality food with less fillers). On rare occasions the reason could be a fluke on the eye but sometimes its a simple as physical damage to the eye by running into something in the pond. Both eyes can have pop eye or just one, either is possible.

Treating Cloudy Eye: Treatments for cloudy eye are a medicated koi food formulated to handle fungal and bacterial issues called MedFinn and or Mela-Fix. Mela-Fix is actually an oil extract from the Melaleuca tree mostly occurring in Australia and it has natural anti-bacterial properties.


Unfortunately, leeches aren’t just looking for a free ride but also a free meal and eventually they will cause mortality of the host fish if left untreated. Leeches can also transmit the koi disease known as SVC. If you think your koi may be victims of leeches you can actually see them on their bodies as the leeches are not microscopic but other symptoms include a darkening or paling of the color of your koi as well as lethargy.

Treating Leeches: Some treatments for leeches include a product called Masoten which comes in powder form. Another product is called malathion however many recommend against this treatment as it is an organophosphate insecticide and though it will kill leeches it may also harm your koi in the process.


Ulcers on the skin of your fish result from bacterial infections that form on scales, causing them to become red. The infection causes holes, or ulcers on the exterior of the fish and will eventually result in loss of scales if left untreated. These ulcers are most often caused by poor quality of the water in the pond coupled with depressed koi immune systems in Spring get attacked by parasites carrying bacteria.  

Ulcer Treatment: Maintain a healthy, clean pond and treat ulcers with a topical antibacterial such as Panalog to stop the bacteria in their tracks.

Saprolegnia Fungus

One of the most common fungal infections found in Koi fish comes from the Saprolegnia fungus. Spores from the fungus can grow on any part of the fish, including its gills. The fungus first attacks the fish by germinating on dead tissue. The fungus has thread-like hyphae that release a substance that breaks down the tissue. As the fungal infection grows, these juices begin breaking down and destroying living tissue.  It often appears like cotton wool and may be stained green from algae.  It almost never attacks a healthy fish –typically the koi will already have some sort of breach like an ulcer.

Treating Saprolegnia

The afflicted fish will need to be isolated in a quarantine tank with the temperature raised to at least 77 degrees F.  Additionally, it will be very beneficial to also get your salt levels up to around 0.3%.


One of the easiest protozoan parasites to see under a microscope, and subsequently confirm your fish is infected, is Trichodina. An infection of this parasite can be detected by a gray-white opaque appearance on the body of infected Koi. Trichodina is a warm water parasite and can survive in the water for a considerable amount of time without a host. Visually, they are perfectly round with hundreds of little hooks that look like cilia. It rotates continuously as it moves through mucus, causing damage to the Koi’s tissue. This parasite attacks both the skin and gills of your Koi. Infected fish also often show symptoms such as flashing, rubbing and lethargy.

Treating Trichodina: Treat this disease with a five day course of increased salinity (0.5 to 0.6%).   Due to increasing tolerance of some organisms to salt treatments a course of formalin may be necessary.

Koi Herpes Virus (KHV)

This virus is a potent one.  Some of the effects of this disease are sloughing off of the skin which leaves the koi vulnerable to bacterial infection.  Your koi will be lethargic and have sores and lesions on its skin, gills and fins.  Because some diseases have overlapping symptoms, gill lesions are one of the more definitive indications of KHV.  This virus is contagious and carries and high mortality rate so treatment needs to be swift.

Treating Koi Herpes Virus: Increase salt concentration to around 0.45% and bring the water temperature up about 1 degree F every hour until it gets to 87 degrees. The fish should remain in this situation for 4 days during which medicated food such as MedFinn should be fed. 

Gill Maggot

Another parasite sometimes infecting Koi is the gill maggot. The parasite most often attacks the Koi’s gills and has a maggot-like egg sac appearance. It is a relatively uncommon parasite sometimes found in Koi ponds but when present, can cause Koi quite a bit of irritation. You will notice the koi flashing and subsequently the gills become less efficient at absorbing oxygen. The most obvious sign of infection is seeing a Koi gasping for air at the surface of the pond.

Treating Gill Maggots: The product Lice-Solve has been shown to be effective against gill maggots (as well as argulus) but you will need to increase aeration.  You can treat the whole pond or individual fish in quarantine.

Bent Koi

Pond owners may sometimes notice that one of their koi is taking on a bent appearance.  There may be a few explanations for this: 1) scoliosis from lack of ascorbic acid in their diet 2) electrical discharge into the water and 3) internal air bladder infection.  Scoliosis can be treated by feeding your koi foods high in Vit. C like yellow bell peppers or kale.  Electrical discharge into your pond may come from submerged pumps that are damaged or otherwise not operating properly and leaking electricity into the water -these discharges can be easily tested for.  A swim bladder infection will most likely require antibacterial injections by someone with injection experience.


Clearly there are quite a few little “beasties” out there that can make life miserable for your koi however there are a good deal more treatments these days as opposed to say 100 years ago. Also, because the treatments are more potent these days there is a good chance that you can deal with a disease or parasite quite rapidly and not lose your prize breeding stock -or even just your favorite koi.

As mentioned previously, the two manuals I recommend having around for quick reference on disease are:

manual of koi health     and        Erik johnson koi health and disease



Posted in Koi Diseases | Tagged anchor worm, bent koi, cotton wool, dropsy, epistylis, fungal infection, gill maggot, gyrodactylus, ich, koi diseases, lymphocytis, MedFinn, oodinium, saprolegnia, skinny disease, trichodina, ulcers | 236 Comments

Top 15 Reasons to Have Koi and a Koi Pond


Koi swimming

Koi in a backyard pond

Enjoying Koi pond in your backyard not only provides a charming attraction to your visitors, but it’s also a great way to relax and rejuvenate at your home. There is something wonderful about enjoying the elegant view of fish and water along with hearing relaxing and tranquil sounds of the water. Many of us don’t look past the reality koi fish are an incredibly rich source of protein and is a wonderfully healthy food. As well as the raising of koi for food you can delight in a koi pond for its several other joys. Let’s have a look at some of the features of having a koi pond on your property.

  1. Aesthetic appeal: Nobody can deny the aesthetic appeal that these ponds can bring to your property. It doesn’t matter, whether you have hired a high-end designer to get these ponds designed or you may have designed the ponds yourself, a Koi pond can add an unparalleled elegance and style to your property or garden.
  2. Nature friendly: When you add a Koi pond to your backyard, it will also encourage the growth of eye-catching and colorful plants near the pond that will attract butterflies and birds, thus creating your own natural and peaceful space.
  3. Improves your real estate value: Any real estate agent will tell you that having a Koi pond in your backyard can enhance the marketability and real estate value of your property however the value of your property is dependent on the individual buyers interested in your property. 
  4. Normalizing your blood pressure: Having a Koi pond in your garden is one of the biggest stress relievers. Since stress is responsible for a number of heath ailments such as high blood pressure, certain heart conditions and anxiety disorders, you can help to reduce these problems by adding a Koi pond in your yard.
  5. Make money by selling Koi fish: Koi fishes are one of the most in-demand fishes and you can easily sell them at substantial profits. Selling them is easy; just participate in any fish show and sell your fish stock to interested buyers.  One of the highest prices paid for a koi was actually $850,000 but in most cases a good size koi with desirable colors and patterning will fetch a couple hundred dollars each.
  6. Symbol of style: If you have a Koi pond in your garden, it is a symbol of your style and helps you to add a certain element of elegance to your garden.
  7. Faster recovery for stroke patients: Studies have shown that the stress free environment provided by Koi fish ponds can lead to a faster recovery for stroke victims.
  8. Pleasure and entertainment for the whole family: There is something unique about watching these colorful creatures. Your whole family, especially kids, will find this really fascinating.
  9. Brings good luck: Japanese people believe that the Koi is a mystical fish that can bring fortune and good luck to any home.
  10. Get rid of negativity: Beautifully designed Koi fish ponds and the magical sound of water can relax and amaze you at the same time. This is enough to reduce any negative or depressive feelings.
  11. Koi fish can eat right out of your hand: You can place food on your hand and then lower your hand slowly; you will be amazed to see Koi fish eating out of your hand. This lovely gesture makes them even more endearing.
  12. Owner friendly pets: If you want to own pets but you don’t have any time to take care of them, then having a pond in your yard with Koi fish would be the perfect solution for you. 

    most popular pets

    According to, the most popular pets by numbers are freshwater fish.

  13. Get rid of insects and flies: Mosquitoes and flies are common problems with a garden, but if you add a Koi fish pond in your garden, you can effectively get rid of these nuisance-causing creatures.
  14. Koi fish ponds are easier to maintain: You can use some natural and easy methods to maintain and clean your Koi ponds. These methods include adding barley straw extract to the pond, reducing the feed and adding beneficial bacteria, among others.
  15. Great source of protein and micronutrients: Koi fish provide you the highest quality protein with many essential vitamins and minerals. In addition, Koi fish are an excellent source of healthy fatty acids.
Posted in General Koi Information | Tagged beauty, good luck, health, insect control, koi, koi pond, protein, real estate value, sell koi | 2 Comments

The Most Effective Tips for Koi Pond Maintenance

koi pond water testing

Koi Pond Water Testing

Having a Koi pond at your home is undoubtedly the quickest way to reduce stress and anxiety that you have to deal with on a regular basis. This peaceful and quiet place is essentially a man-made paradise. Apart from eliminating stress and tension of your mind, a Koi pond is a perfect way of adding beauty to your backyard or any outdoor space.  However, it requires some effort to keep it in its healthiest and most attractive condition. You may have heard that building a Koi pond is a much easier task as compared to maintaining it. However, if you take proper care of your Koi pond right from the beginning, you can avoid many complications later on. With that in mind, let’s take a look at some of the most simple and effective precautionary steps that you can employ to keep your Koi pond healthy.

Perform constant water checks to avoid common problems

Koi pond owners may have to deal with issues like acid rain, excessive fish waste and nutrient-enriched runoff.  In order to stay on top of these common but serious issues, it is highly advisable to perform constant water checks. Although it’s true that Koi fish can be easily taken care of, poor water quality can cause even the hardiest fish to suffer from health issues.

Maintain the right temperature

People living in colder regions where ponds freeze over shouldn’t worry-they will be relieved to discover that Koi can survive during the winter months . When ice forms on the surface, these fish can essentially hibernate under the surface. In order to be on the safer side you can use a floating de-icer to maintain the a hole in the ice for proper gas exchange.


Avoid overfeeding

Over feeding your Koi is one of the most common yet unhealthiest mistakes made by well-intentioned koi owners. When feeding you should take that opportunity to evaluate your Koi closely. This will help you to detect any diseases or injuries that have occurred to the fish. Overfeeding can lead to poor water quality which itself can initiate a host of  additional problems down the road.  These problems include high ammonia and nitrites in the water which can translate into fin rot, parasites and other diseases


Properly maintain all your Koi pond equipment

This equipment normally includes a good quality filtration system, a powerful pump, protein skimmer, aeration system and ultraviolet sterilizer. For instance, the pond pump is used for pumping water in and out of the pond which aids in maintaining proper water movement in the pond.


The filtration system in combination with the protein skimmer is very useful in keeping the surface water clean. As mentioned previously, a floating de-icer can be useful in maintaining proper gas exchange in the pond during the colder months.


There is no doubt that Koi fish are one of the most graceful aquatic pets.  In fact, in the US koi are the most common fish pet.  Interestingly,  they also have an fairly decent life span (you can expect 15-20 years and in some cases much longer). However, if you don’t take proper care of them, they won’t be able to live to their potential.

For a more comprehensive coverage of koi maintenance click here.

Posted in Koi Care Information | Tagged Avoid overfeeding, constant water checks, Maintain the right temperature, maintain your Koi pond supplies | 159 Comments

History of Koi Ponds

Vintage Koi Painting

Vintage Koi Painting


The term “koi” is derived from a Japanese word “nishikigoi”, which literally means brocaded carp. These include the ornamental varieties of common carp, which are used for decorative purposes in outside water gardens and koi ponds. However, “koi” is more of an English word and includes both brightly colored as well as dull, gray fish varieties. Koi, in Japanese, means love, affection or friendship. Hence, ‘koi’ are used as a symbol of love and good luck.

The exact origins of today’s koi are still unknown, yet there is a common belief that they originated around the areas of Western Asia and Persia. The carp exhibits exceptional capabilities to survive and adapt to a wide range of water conditions and climates. Owing to this reason, the common carp, found its way into Japan and China by means of natural waterways or trade.

Origins of Koi Breeding

It was discovered that the protein content of carp was very high. To that end, the rice farmers situated in the Niigata Prefecture, began with the harvesting of carp, so as to sustain themselves during the long winter months. Around the middle of the 18thcentury, these farmers observed certain kind of mutations (consisting of red and white blotches on the scales) on the carp. Then, these mutated fishes were separated from the ordinary ones, and selectively bred. This was the first instance of koi breeding, and after this it became quite a pop

ular activity. In the 19th century, koi breeders exhibited their prized possessions in Tokyo, where people from all over Japan were present to take a look at these “living jewels”.

Raising Koi gains popularity

Over the years, breeders started coming up with new and different koi varieties. Koi enthusiasts could be found in every corner of the world. Many people went by the Chinese belief that koi brings in ‘ong’ which means, luck. Hence, they would build small koi ponds outside their homes as a part of feng shui, so as to fill their lives with good luck and prosperity. For others, having a koi pond in the backyard was more of a fun and relaxing thing to do. Regardless of the basic purpose, nothing could beat the charm and beauty of having a koi pond on one’s property.

Why Koi are revered

Koi are a highly social and playful variety of fishes. These are ideal for the water garden or a backyard pond as they are playful, hardy, beautiful and love to be hand fed. When you are in the process of choosing a koi to be added to your backyard pond, make sure to pick the variety of fishes which are active and friendly. Avoid fishes that show any signs of injury or are isolated.

The greater amount of time you spend with your koi, the more you will be able to observe their individual personalities and traits. Some koi varieties can have a life span as long as humans. In addition to this, keeping koi in a well maintained environment is also important in order to ensure that your fishes remain healthy, alive and playful.

Posted in General Koi Information | Tagged carp, china, japan, koi, koi breeding, koi history, love, luck, mutations, Niigata Prefecture, ong, persia, raising koi, western asia | Leave a comment

Welcome to Koi-Care dot com

This site is meant to inform those that need to learn more about their fish, their pond or water chemistry. If you have any questions regarding koi or ponds please write in using my contact form!


Posted in Koi Care Information | Tagged koi breeding, koi care, maintenance, pond building | 3 Comments