Best Treatment To Treat Flukes In Koi | Aquascape Addiction

Best Treatment To Treat Flukes In Koi

As an Amazon Associate I earn from qualifying purchases.

We cover the best treatments to treat flukes in Koi and pretty much everything you need to know about this disease from how to identify it, symptoms and prevention methods.

Best Treatment To Treat Flukes In Koi

There are certain problems that arise from having an outdoor pond with outdoor fish that are exposed to elements that are not present within an indoor aquarium. There are various bugs and parasites that can make their way into the water, this making your pond koi very sick.

One of these parasites is known as flukes, and they can definitely wreak havoc on your koi. Today we are here to talk all about koi in flukes, how to identify flukes, what the symptoms are, preventative methods, and treatments too. The main purpose of today’s article is to help you find the best treatment to treat flukes in koi (this is our top pick).

How To Indentify Flukes

First and foremost, the problem with flukes is that it is a parasite that is microscopic. It is not something that you can see with just your eyes, as they are way too small for the naked eye to be able to detect. In order to actually see flukes with your eyes, you will require professional equipment, or in other words, a high quality microscope.

If you have a good microscope, identifying flukes is not very hard. However, chances are that you don’t want or have a microscope, especially seeing as high quality ones are very expensive. So, if you don’t have a microscope, the only real way to identify flukes is by observing your koi fish.

You need to look for symptoms and signs that are commonly associated with flukes parasites. We will be getting into identifying the two major types of flukes and the symptoms associated with both of them just a little later on.

Being able to spot the symptoms in your koi fish is the best way to identify flukes. Your fish will change in appearance and behavior if it suffers from flukes, so if you catch it early enough, you should be able to treat it without too many long lasting consequences.

Best Treatment To Treat Flukes In Koi

Here we have three different treatment options to get rid of flukes in koi. As far as we can tell, all of them qualify as the best treatment to treat flukes in koi. Generally speaking, they are medicinal grade treatments that work to kill the flukes parasites while also healing your fish at the same time (this one is our top pick).

Remember folks, these are parasites, so besides real medicine, there are not really any other treatment options, so you will definitely want to take a closer look at the flukes treatments below.

By the way, there is really not much to say about any of these following options other than that they are specifically designed to kill flukes and sometimes other parasites too, so this is going to be short and sweet. Just so we don’t repeat ourselves 3 times over, always make sure to follow the proper dosing instructions as labeled on the specific treatment in question.

1. Hikari Prazipro

This is generally considered to be one of the best options for koi flukes treatment (you can check the current price here). It is intended to kill koi flukes parasites, turbellarians, flatworms, and tapeworms too. It is also intended to treat the symptoms cause by flukes including irritation, redness, and ulcers. Most people would recommend this as the number one treatment.

Click here to buy Hikari Prazipro at Amazon

2. Broad Spectrum Disease Treatment

This is another really good option to go with, one that is intended to treat flukes and so much more. This stuff can be used for Ichthyophithirius (Ich), Chilodonella, Costia, Oodinium, Trichodina and fungal infections, plus of course for parasitic infections like flukes as well. The only thing to remember here is that you should not use this stuff with other medications.

Click here to buy Broad Spectrum at Amazon

3. Aquascape Praziquantel Treatment

This is a good option too, one that will not stress fish or mess with filtration. It is meant for all kinds of parasites including flukes. This stuff works for both internal and external parasites, which is always nice. One container can treat up to 1,250 gallons of pond water.

Different Types Of Fluke Parasites

Ok, so as we mentioned before, there are actually two different types of fluke parasites and they both affect your koi fish in different ways. They are a part of the same parasite family and the symptoms they can cause are often similar, but the areas of the koi’s body which they affect tend to differ.

Let’s talk about the two types of fluke parasites, what they do to your koi, and how you can identify them before it is too late.

Gill Flukes

Gill flukes is the type of flukes that is most commonly seen and heard about. They tend to be easier to identify, both in terms of their appearance and symptoms, than the other type of flukes, skin flukes.

This is mainly because they tend to be larger than skin flukes, up to 3 mm in length. However, to properly see them, you will still need to have a microscope because they are too small to clearly see with the naked eye.

They are mostly transparent, they are long, slender, and have a round body shape. They also have dark spots on their heads, which skin flukes do not have. You will also be able to see a set of hooks which gill flukes use to attach themselves to the gills of your koi.

As the name implies, gill flukes like to attach themselves to the gills of your fish, where they like to feed off the gill tissue and mucus which is excreted by the gills. They can cause ulcers, irritation, and open wounds.

Let’s quickly take a look at the symptoms which your koi will exhibit if it is afflicted with gill flukes.

  • Lack of appetite – not eating.
  • A dulling in the color of your koi.
  • Being very shy and hiding all of the time.
  • Have irritated and red gills.
  • Ulcers on the gills.
  • Constantly chewing even when there is no food.
  • Rubbing itself, especially the gills, against objects in the pond.

Skin Flukes

Skin flukes are much harder to see than gill flukes. This is because they are much smaller, only about 0.4 mm in length, plus they are transparent for the most part, making them impossible to see without a microscope.

They do have the hooks used to attach themselves to your koi, just like gill flukes. However, unlike gill flukes, skin flukes do not have black dots on their head, which is the easiest way to tell them apart.

One of the really bad parts about skin flukes is that they reproduce and bare live young, which means that they don’t lay eggs, and as soon as the young are born, they will search for koi to inhabit.

As the name of these things imply, as opposed to attaching themselves on or in the gills of your koi, they hook onto any part of the skin, usually on the body. They will usually always be on the outer scales. So, in terms of identifying flukes, what symptoms will your koi exhibit when afflicted?

  • Not eating & lack of appetite.
  • Rubbing its body against various items in the pond.
  • A dulling of coloration.
  • Being shy and hiding.
  • Having irritated skin.
  • The formation of ulcers.

Where Do Koi Flukes Comes From?

You may be wondering where koi flukes actually come from, which is a very fair question no doubt. The problem with these parasites is that they can come from many different places and are often already present in your pond water.

Chances are that the flukes were in the pond water, or somehow migrated from surround animals, plants, and other wildlife. Heck, the flukes could have already been in the water when you put it in the pond.

However, generally speaking, the biggest and most prominent source of koi flukes in ponds is from other animals, specifically predators that come to eat your koi. Herons and ducks that come to hunt your fish are the biggest culprits here.

The flukes may be present on their eggs, in their feces, or in their feathers. Whatever way the parasites got onto the duck or heron, as soon as those birds come to your pond in search of a snack, they will transfer the parasites to your pond and thus to your fish.

Flukes may also be present on new fish that you add into the pond. The problem here is that identifying flukes in the early stages, especially on a young fish, can be nearly impossible. Flukes may also be present on various plants or other decorations that you insert into the pond.

As you can see, flukes can make their way to your koi fish through many different delivery methods, which is a problem no doubt. The trick is to identify the symptoms fast and to treat them ASAP.

How Do Flukes Harm My Koi Fish?

Ok, so for the most part, koi flukes on their own will not actually kill your fish, at least not very fast. As we mentioned above, the most common symptoms of flukes are things like a lack of appetite, hiding, rubbing on decorations, and having irritated skin, wounds, and ulcers. These things are not necessary fatal, except for open wounds and ulcers, which if left untreated for a long time can cause some really serious problems.

The biggest problems caused by koi flukes are those of secondary infections. For one, since flukes cause koi to not eat right, plus to be in pain, their level of stress will be greatly increased, they will be malnourished, and their immune systems will be compromised. All of these things can lead to fatal consequences in one way or another.

However, the stress and the compromised immune system are the biggest issues because they leave your koi open to being infected by any number of other bacteria, viruses, and parasites in the water. Therefore, koi flukes are actually quite dangerous, not necessarily on their own, but due to the fact that they render your fish much more susceptible to a host of other problems.

Can Flukes Live In Cold Water?

The problem with flukes is that they are very resistant and resilient parasites, ones that are not affected greatly by temperatures. The problem with koi flukes is that they can survive in cold water as long as it is not freezing. You see, fluke eggs take around 4 days to hatch when the water is warm.

However, when the water is cold, they can take up to 6 months to hatch, or just until the water warms up with the seasons. This is a problem because fluke eggs can remain dormant on or in your fish for several months before they hatch and start causing problems. Therefore, the answer to the question is yes, flukes can live in cold water, but the eggs won’t hatch until the water is warmer.

A good thing to do here is to treat your pond for all kinds of parasites and bacteria before the winter hits. This way you can ensure that a koi flukes outbreak does not occur once the winter is over. In other words, you should winterize your koi pond before the temperature drops and winter hits.

Should I Quarantine A Koi With Flukes?

If you notice that your koi are suffering from flukes in the early stages, or you have just a couple of fish that have been infected, it is probably easier to just treat the whole pond. If you notice that one fish has early signs of flukes, chances are that the parasites have already migrated to the other fish. Therefore, quarantining certain fish is useless. It is much easier to just treat the whole pond at once.

However, if you have a koi that is suffering from advanced stages of flukes, and even has ulcers, you might want to put it in a separate quarantine or holding tank. This way you can closely monitor it, treat it, and also treat for secondary bacterial, viral, or parasitic infections that may occur.

Once again, if you notice that all of your koi fish have advanced flukes, you may as well just treat the whole pond at once. Quarantining is really only effective if not all of your fish are affected by flukes (more on quarantining here).

Tips To Prevent Koi Flukes

There are quite a few steps that you can take in order to help prevent koi flukes, so let’s go over these steps right now. If you follow most or even all of these tips, you should not see a problem with koi flukes any time soon.

Keep Predators Away

One of the most effective ways to prevent koi flukes is to keep predators at bay. As we mentioned before, koi flukes often make their way into a pond thanks to birds, usually ducks or herons, but others can bring flukes too. Therefore, you need to keep those animals away from your pond. There are quite a few different ways of keeping birds away from your pond. Using a pond net can definitely help a whole lot here.

One thing that you can do is to dye the water a deep shade of blue, green, or even black. Pond dyes are well known for providing some camouflage for your fish so the birds cannot see them and will therefore not be attracted to the pond.

Some people also put a bunch of bird feeders and bird baths in their yards, well away from the pond, in order to get the birds to go to the feeders instead of the pond. You can also try using some scarecrows or statues of large predatory birds.

Ducks, herons, and other birds also hunt your fish, thus causing them stress and injuries, and therefore rendering them more susceptible to parasitic and other secondary infections.

At the same time, birds that defecate in your pond will contribute to ammonia and bad bacteria levels, both of which help parasites like flukes thrive and multiply. So, keeping predatory birds and other animals away from the pond is a really big deal here.

Maintain Pristine Water Quality

Parasites like flukes tend to thrive in bad water conditions. Water that is full of ammonia, nitrites, fish waste, and decaying organic matter is the perfect place for parasites and bacteria to thrive and multiply.

Therefore, keeping the water really clean is a big deal in terms of preventing koi flukes outbreaks. You need to make sure that you have a water pump that can easily handle the entire water volume of the full pond every hour.

At the same time, you need to have a really good filtration unit that engages in all 3 major types of filtration including mechanical, biological, and chemical filtration. You need to make sure that your filter removes all kinds of debris, rotting food, decaying plant matter, ammonia, nitrites, and other unwanted compounds from the water.

The less of these things are in the water, the harder time the flukes will have surviving and multiplying. Flukes feed on ammonia and waste, so this is important.

You need to test the water quality at least once a week to measure for organic compounds, specifically ammonia and nitrites. You also need to perform regular water changes, at least 25% once per month.

You also need to have sufficient biological filtration, which is probably the most important part, because biological filtration helps to remove ammonia from the water, which flukes live to feed on and live in (if you don't have a filter then see this article). Maintaining good water quality is also important for keeping your fish healthy. The right plants can also help keeping your pond water clean, we have covered our favorite plant picks here.

Koi Health, Stress, & Feeding

Like we just said, water quality is not only important because of the conditions required for flukes to live and multiply, but also because of the stress levels and immune system of your koi.

The worse the water conditions are, the more stress, the unhealthier, and the worse the immune function of your koi will be. Therefore, dirty water renders your fish more susceptible to being infected by flukes, and therefore also more susceptible to secondary infections.

You also do not want to overstock the pond. For one, overstocking the pond with too many fish can cause territorial issues, spatial issues, and can end up stressing your koi out. At the same time, the more fish there are in the pond, the heavier the bio load, the more waste and ammonia will be created, thus creating ideal conditions for flukes.

Another big thing to keep in mind here is that you need to make sure that you are feeding your koi properly. For one, don’t overfeed them, because they will produce more waste and therefore more ammonia, plus uneaten and decaying food will also produce ammonia.

Also, feed your koi a well-balanced diet that meets the nutritional needs of the fish. The better the food they eat, the happier and healthier they will be, thus assisting in the fight against flukes infections (we have covered our top 10 Koi foods over here).

Winterizing The Pond

The other thing that you want to do is to winterize the pond that your koi fish are in. Koi fish do something that resembles hibernation during the cold months. This means that their bodily functions slow down and their immune systems become weaker. Feeding your koi a proper diet and keeping them healthy throughout the warmer months will ensure that they are in top health for the winter.

There are several things that you should do to effectively winterize your pond besides keeping your koi healthy before the winter. For one, do a thorough cleaning before it gets cold. This means cleaning the plants, rocks, decorations, changing water, cleaning the filter, and all of that other fun stuff. Having a de-icer (we have reviewed some good options here) and an aeration pump ready for the winter will help too.

You can also do some preventative treatments for the most threatening parasites and bacteria before it gets cold. This way you will kill off bacteria and parasites before they get a chance to pop up and wreak havoc once the temperature rises again. On that same note, you might also want to add some beneficial bacteria into the pond that are specially designed for the winter, as they will help keep ammonia and nitrite levels low.


As you can see, while flukes on their own are a nuisance, the secondary problems they can cause can be fatal, and fairly quickly at that. Therefore, you want to make sure that you can identify the symptoms and take proper steps for treatment as soon as possible. Remember to maintain good water quality and keep your koi healthy to give them the best chance. The best treatment to treat koi in flukes is usually preventative, not reactive, although you may not have a choice but to use reactive measures like medicines.