Do Koi Fish Have Parasites?

-- By Carol

You may have seen koi fish swimming in ponds and thought they were beautiful. If you’re a fan of koi fish, you may be wondering if these beautiful creatures are susceptible to parasites.

In this blog post, we’ll take a closer look at koi fish and parasites, and what you can do to prevent your koi from becoming infected.

Keep reading to learn more!

Table of Contents

Do Koi Fish Have Parasites?

Yes, koi fish can get parasites. Like every living creature, parasites, illness, and disease are inevitable to the koi fish.

Kept in a pond, in an open environment, koi fish are bound to get parasites at some point in their lives.

There are two main types of koi parasites, internal and external.

Internal parasites include tapeworms and flukes, external parasites include Anchor worms and leeches.

Though it might sound scary, as parasites can be a horrifying thing for the koi population, the good news is that koi fish are very resilient.

If you properly care for your koi pond, the chances of koi getting sick because of parasites are pretty low.

So, keep an eye on the pond’s water quality and the koi fish’s movement and get it treated as soon as you see scum or dirt on the water.

In this article, we will be teaching you everything there is to know about koi fish and parasites so you can prevent them.

Also read: Why Is My Koi Fish Flashing? Possible Reasons!

What Do Parasites Look Like in a Pond?

Most koi parasites look like small, water-dwelling creatures and are hard to see with the naked eye. They can either appear in the form of little white worms or black dots on the water’s surface.

On the other end, large pond parasites such as tapeworms and flukes look like a thin thread attached to the koi fish’s body.

When a parasite attacks a koi fish, it starts laying eggs on the fish’s scale.

So if you see white spots on your koi fish, or they are lethargic, have damaged fins, swollen skin or sore skin, they have it.

Are All Little Worms in the Koi Fish Pond Dangerous?

No, not all kinds of worms in a koi fish pond are dangerous. While some can be parasites, Limnephilus Hirsutus can also be found in the koi fish pond.

Limnephilus Hirsutus are tiny organisms that keep the pond water neat and clean.

Why Do Koi Fish Get Parasite?

Parasites are a natural part of the aquatic habitat. However, only a few are parasitic to the koi fish. In fact, the majority of parasites (worms) are ‘free livers’ and do not harm the koi.

Parasites like chilodonella, costia, and trichodina are free-living species that peacefully co-habitat with koi.

On the flip side, leeches and fish lice can be dangerous for the koi. These kind of parasites are usually introduced by animals and water birds as they carry them from one pond to another.

The presence of fish lice and leeches is a clear indicator that an unhealthy pond is near your koi fish pond, so you need to be on your toes.

Pond plants can also be a source of parasites, especially if they have been transferred from an infected pond.

Summing it all up, although parasites are natural, an unhealthy pond environment, poor quality of water, and interaction with infection-carrying animals can lead to an infestation.

Does My Koi Fish Have Parasite? How Do I Know?

Parasite infestation is very common in a koi fish pond. The two categories of koi parasites are as follows:

External Parasite in Koi Fish

External parasites attack the skin of koi fish or the gill filaments, making them easy to identify. The symptoms of an external parasite infestation include:

Increased mucus production.
Respiratory distress.
Pale gills.
Clamped fins.
Redness sores.
Ulcers on the skin.
Weight loss.
Constant rubbing against objects.
Erratic swimming.

Internal Parasite in Koi Fish

Finding their way inside the koi fish’s body, internal parasites usually attack a koi’s digestive tract or tissues.

Because the symptoms are less visible, this makes identification of an internal parasite infestation in a koi fish pond difficult.

Symptoms of internal parasites in your koi fish include:

Loss of appetite.
Swollen belly.
Slower growth rate.
Lethargy or sluggishness of the koi.
Muscle loss.
Weight loss.
Lower reproductive rate.
Intestinal infestation.

Whether external parasites or internal parasites infest your koi fish pond, it is advised to seek a professional’s help as they will help you in determining the most effective treatment for your koi fish.

How Do I Check My Koi Fish for Parasite?

If your koi fish has discoloration, is covered with a gray mucus layer, or is flicking around the pond, the koi fish pond is infested with parasites. In order to be sure, you will need the following equipment:

Oxygen and filters.
Swabs and tweezers.
Microscope and slides.
Water/temperature monitoring tool.
Standard koi pond chemicals – Potassium Permanganate.

Once you have everything you need, follow the below-mentioned guide to identify a potential parasite threat in your koi fish pond:

Step 01: Stand at the edge of the pond and carefully observe your koi. If you notice mucus or discoloration on your koi, use swabs and tweezers to take a skin scrape.

Step 02: Now take a clean microscope slide and carefully place the scrape of the koi’s skin on it. Cover the slide and place it under the microscope.

Step 03: Look through the microscopic lens to check for parasites. Repeat the above-mentioned steps for two to four koi fish. In case you haven’t done this before, we recommend asking a professional.

In case there are parasites in the sample, the pond’s water quality is extremely poor, and there’s a high chance that the entire koi population might be affected.

Use a temperature and water monitoring tool to check the exact temperature and volume of the water.

Once you have all the essential readings, consult a professional to know which water treatment and pond chemical should be most effective.

Don’t forget to wear gloves when testing the koi fish pond for parasites, as direct exposure to the microorganism can harm you.

Common Types of Koi Fish Parasites | How Do I Treat Them?

Not all parasites are the same. This makes it essential for you to know the difference between each parasite, its symptoms, and its unique treatment requirements.

1. Dactylogyrus (Gill Flukes)

Gill Flukes is a microscopic worm that cannot be seen by the naked eye. A koi infected by Dactylogyrus will show rub against rocks or jump out of the water frequently.

Dactylogyrus is very similar to fleas that infect dogs and cats. Potassium permanganate solution and Fluke Solve are the best ways to treat Dactylogyrus.

2. Ichthyophthirius Multifiliis (Ich)

Also known as the “White Spot” disease, Ichthyophthirius Multifiliis is a microscopic protozoan parasite. It covers the koi’s skin with small white spots, roughly the size of a salt grain.

Ich is a ubiquitous parasite that reproduces quickly. The best way to treat Ichthyophthirius Multifiliis is to mix malachite green with formaldehyde.

Maintain the pond’s temperature and apply the mixture to the koi’s skin for five days. In case it doesn’t work, consult a koi specialist.

3. Lernaea (Anchor Worms)

Anchor worms can be 10 to 12 millimeters long. They usually attach themselves to the koi’s tail and body.

Unlike other parasites, Lernaea needs to be removed manually. All you need is a cotton ball, potassium permanganate, and tweezers.

Dip the cotton ball in the potassium permanganate solution and gently dab the koi fish with it. This will loosen the parasite’s grip, and your koi will be healthy again.

What Should I Do to Get Rid of Parasites in the Pond?

Although there are several ways to get rid of parasites from the koi fish pond, the most common is the use of parasite-control products.

These include parasite control pills, parasite control liquid, parasite control pellets, parasite control food, parasite control bath, and parasite control granules.

Roundworms, tapeworms, and flukes are the most common types of parasites in koi fish. Therefore it is advisable to use products that are specially designed to kill the microorganism.

Once you have successfully killed all the parasites, clean the koi fish pond, replace the water, and install a filter system to minimize the risk of parasite infestation in the future.

Also read: Are Koi Fish Dangerous to Humans?

How Do I Prevent Parasites Infestation in the Koi Fish Pond?

Even though parasite infestation isn’t fatal for the koi, if left untreated, it can be a serious problem. Here are five ways to prevent parasite infestation from the koi fish pond:

Regular Checkup: Make sure you regularly check the koi fish pond for signs of parasites and treat them as soon as you suspect an infestation.
Quarantine New Fish: Make it a habit to quarantine the fish before adding it to the pond. This gives you enough time to check for diseases, minimizing the chances of parasite infestation.
Raise Koi Pond Temperature: Although high temperature helps kill parasites, it can be dangerous for koi fish. zconsult a koi specialist to know the ideal temperature for the pond.
Quarantine the Affected Fish: If you have noticed symptoms of parasite infection in the koi, quarantine the fish as soon as possible.
UV Filter: A UV filter can kill parasites. However, it doesn’t completely remove parasites from the pond.

Final Thoughts

A koi fish pond is full of parasites. However, not all of them are lethal for the koi. While some parasites can be easily visible to the human eye, others are impossible to spot.

Therefore, it is vital to keep an eye on the pond’s water quality and the health of the koi fish and treat them as efficiently as possible.

Look out for lethargy, redness, worms, and swelling, and consult a koi specialist to treat the infected fish right away. Note that any delay in providing the correct treatment can lead to dead koi.

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