7 Worms Found In Fish Tanks (& How To Get Rid Of Them)

Last Updated on 2023-08-08

We all know that fish are not the only creatures that live in water. There are also a variety of invertebrates, including worms. While most types of worms are harmless, there are a few that can cause problems for your fish. . In this article, we will discuss the different worms that you can find in your fish tank. We also mentioned how to identify them and how to get rid of them in your aquarium. More importantly, we gave tips on how you can prevent worms from getting and multiplying in your fish environment.  Keep on reading to learn more!

What Are The Worms In Your Fish Tank?

Worms are creatures that live at night. Just because you can’t see them during the day doesn’t mean they aren’t there. Because they can’t stand the light, they stay in the dark gravel, rocks, plants, or any other place they can hide during the day. Here are 7 common worms that can be found in your fish tank.

1. Detritus Worms

Detritus worms are thin and pointy, and their color is white-brown. They will be in the sand or rocks in your tank. This kind of worm eats dead fish and plant matter, so it won’t hurt your fish. It’s not unusual for an aquarium to have detritus worms, since there are many ways to bring them in.

2. Planaria Worms

Planaria are flatworms that usually get into aquariums through live plants from ponds. Most of the time, they live in natural water sources, but they are easy to move into aquariums. There is a chance that planaria worms will grow in both freshwater and saltwater aquariums.

3. Bristle Worms

Bristleworms might look gross and ugly, but most of them are good for your tank as long as they are not poisonous. They eat things in your tank that would otherwise break down and make ammonia, which makes your biological filter have to work harder. Most of the time, bristle worms get into the tank through the live rock.

4. Anchor Worms 

Young anchor worms are crustaceans that swim freely and burrow into the skin of fish. It takes a few months for the worm to show itself on the fish’s body as holes or sores. The worm dies after it lays its eggs. Since the worm can’t be taken out by hand, it should be cured with a 10ml/l potassium permanganate bath for about 20 minutes.

5. Thorny-Headed Worms

The thorny-headed worm looks a lot like the anchor worm, but it is smaller. It sticks to the fish’s gills. The gills have white or green threads that can be seen. The fish scratches on things in the aquarium all the time. A 20-minute (10ml/l) bath in potassium permanganate is also part of the cure.

6. Flukes

Flukes are flatworms that look a lot like Ick and can be seen more clearly with a magnifying glass. If infected, the fish will have mucus on its gills and/or body, red spots on its skin, and its fins. It also breathes quickly. If you don’t treat flukes, they will destroy the fish’s gills and kill it.

7. Leeches

These external parasites can be seen on the fish’s skin, gills, and fins, and they look like Ick. Since they stick to the fish, the best way to get rid of them is to give the fish a 20-minute bath in a 2.5% salt-to-water solution. Most of the leeches will fall off during the bath, and the ones that stay can be picked off with tweezers.

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How to Identify Worms In Your Fish Tank

Worms in your fish tank can grow quickly, and the same is true for how they have babies. The sooner you get to identify them, the quicker you’ll be able to successfully remove them from the tank. Here are 7 ways you can identify worms in your fish tank.

1. Movement

One of the easiest ways to tell if your fish tank has worms is by observing the fish themselves. If you see any fish swimming erratically or notice them rubbing against objects in the tank, it could be a sign that they are trying to rid themselves of worms. In severe cases, fish may even stop eating altogether.

2. Appearance

Another telltale sign of worms in your fish tank is if the fish appear thin or sunken in appearance. This could be a sign that the worms are stealing nutrients from the fish, preventing them from getting the nourishment they need.

3. Growth

If you notice that your fish are not growing at the rate they should be, it could be due to worms leeching off their food. In addition, fish with worms may have stunted growth or fail to reach their full potential size.

4. Behavior

As mentioned before, fish with worms may swim erratically or rub against objects in the tank. In addition, they may also appear to be listless and lethargic. If you notice any changes in your fish’s behavior, it could be a sign of an infestation.

5. Color

Aquatic worms are commonly white, gray, or reddish-brown and can be found in gravel or plant soil. They move around like an earthworm. You might see only one or two moving in your substrate. Or you could see large groups of them moving.

6. Length

Aquarium worms grow from anywhere between 1/16 to 2 inches in length. You may not be able to see the worms themselves, but you may notice their eggs which are about the size of a grain of salt.

7. Location

Worms can be found in a variety of locations in your fish tank. They may be in the substrate, on the plants, or even in the filter. If you suspect that your fish tank has worms, be sure to check all these areas for signs of an infestation.

Types Of Worms In Your Fish Tank

There are many kinds of worms to look out for in aquariums, from simple flatworms to sharp bristle worms. Below is a list of the different types of worms that can be found in your fish tank.

1. Trematodes – Flukes

Trematodes are the most fundamental types of worms. The skin, gills, and eyes of fish can get extremely irritated by these tiny worms. These parasites, which are often called “flukes,” will be a problem at least once in a fish keeper’s career.

2.  Annelids  – Bristle Worms, Detritus, Leeches 

Most of the worms people are familiar with belong to the group called “annelids.” There are earthworms, polychaete worms, and leeches in this group. Bristle worms are one of the most common types of animals that live in saltwater. Many hobbyists have found these worms by accident when they were cleaning out the tank substrate. 

3. Crustaceans – Anchor Worms  

People call members of the Lernea genus “anchor worms,” even though they may be crustaceans. Anchor worms are very annoying to fish and can spread infections to other parts of the body. But it’s easy to find out what’s wrong with them and treat them.

4. Nematodes – Hookworms and roundworms

Nematodes are one of the biggest groups of worms. They are made up of parasitic, commensal, and zoonotic worms, all of which can affect aquatic animals. Larval migrans is a disease in which the larval stages of nematodes, also called hookworms, move through all of the body’s tissues. This can make people and other animals very sick.

5. Tapeworms – Cestodes

Tapeworms and other cestode parasites that live inside fish are much harder to find. It can be hard to see cestode segments moving through the feces while they are still alive. Most of the time, the most common sign of an infection is a failure to grow or gain weight. A cestode infection can only be confirmed with a fresh microscopic exam of the feces.

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How To Kill Worms In Your Fish Tank

Worms in your fish tank can be a big problem. They can reproduce quickly and make a mess of your tank. But there are some things you can do to get rid of them.

1. Add Snails

The first thing you want to do is remove as many worms as you can from your substrate. If you have a lot of worms in your fish tank, you might want to add a couple of snails because snails naturally eat detritus worms.

2. Stop Overfeeding

Don’t feed your fish too much, because the extra food will go bad and might turn into more worms. Overfeeding your fish, especially with flake food that breaks down quickly, is another common cause of worms. Make sure you’re giving your fish the right amount of food, and if you can, switch them to pellets.

3. Remove Dead Plants

Do not leave dead plants on top of your substrate. It can be just as bad for them to rot there before you can get them out of the tank. Worms do well in dirty places with rotting dead plants. They can show up in your tank if you don’t clean it regularly, get rid of dead things, and change the water once a week. 

4. Take out Uneaten Food

Make sure you take out any food that hasn’t been eaten. If you don’t, it will just pile up and encourage worms. Worms like Detritus would feed on uneaten food. This will cause them to rapidly reproduce in your tank.

5. Rinse Your Plants

You should rinse all of your plants before putting them in the tank. Make sure they don’t have any worms on them. You may use some chemical dip to kill worms before adding them to your aquarium. 

6. Clean Your Gravel

If you have gravel on top of your substrate, you should take it out and clean it before putting it back in the tank. This should get rid of any worms that might be there. It’s important not to use gravel from another tank because it might still have worms in it, which you don’t want to put in your current tank.

7. Add Snails 

The last thing you can do is put snails in your tank. They will eat any leftover food and trash that aquarium worms like to eat. However, make sure to do your research to make sure you’re adding the right type of snails for your tank environment.

How To Remove Worms In Fish Tank Filter

It’s important to keep your fish tank clean, and one way to do that is by regularly removing worms. However, sometimes worms can get into your filters. In this section, we’ll go over 7 steps you can do to remove worms in a fish tank filter.

1. Pull the Filter’s Plug

Make sure to unplug any equipment that could get broken while you clean the tank. This will help avoid any accidents while cleaning the filter.

2. Get the Buckets Ready

Prepare two buckets for separating the gravel and water. Put the gravel with the worms in one bucket and put the clean new water in the other. 

3. Pull the Worms out 

Use a gravel siphon to get the worms out. Make sure that the tank doesn’t lose too much water. Cover the mouth of the siphon with your thumb until it is under the surface of the gravel. Most worms live in gravel, so when you remove the gravel, you also remove the worms. 

4. Clean the Vacuumed Gravel

Clean the siphoned gravel to kill two birds with one stone. Use a clean basin and a mix of 5% bleach in hot water and leave it for around 10 minutes. The solution will get rid of the slimy algae and fish food that hasn’t been eaten. Make sure to rinse the gravel four or five times with hot water to make sure that none of the bleach sticks to it. 

5. Return Everything To The Tank 

The last step is to put everything back where it belongs in the tank. Put the clean gravel back in the tank, close the filter, and make sure the pH and salt levels are right.

6. Do a Water Change 

After you’ve put everything back in the tank, do a partial water change. This will help to get rid of any residual bleach and make sure the water is clean for your fish.

How To Prevent Worms In Your Fish Tank

Only prevention is better than treatment. Worms don’t need to be in your tank in the first place. You can learn how to keep them out. Below are some ways to prevent worms from getting into your tank:

1. Quarantine New Plants or Fish

Inspect new plants and fish before adding them to your tank. If you see any worms on them, don’t add them to your tank. Dip them in a deworming solution or remove the worms manually.

2. Don’t Overfeed Your Fish

Worms are attracted to uneaten food. Overfeeding your fish can cause worms to infest your tank. Feed your fish only as much as they can eat in a few minutes.

3. Keep Your Tank Clean

Worms thrive in dirty tanks. Do a partial water change every week and clean your tank regularly. This will help keep the water quality high and make it less inviting for worms.

4. Use a Dewormer

You can use a dewormer to prevent worms from getting into your tank. Add it to your tank according to the instructions on the package. There are also deworming solutions that you can dip new plants and fish in.

5. Get Rid of Dead Fish

Worms often enter tanks through dead fish. If a fish dies, remove it from your tank as soon as possible. You may want to quarantine new fish before adding them to your tank. This will give you time to watch them for signs of worms.

6. Get Rid of Dead Plants

Dead plants can also attract worms. Remove them from your tank as soon as possible. Keep  your tank clean and free of debris to prevent worms.

7. Avoid Overstocking

Worms can also enter tanks through overstocked fish tanks. This is because the water quality deteriorates quickly in these conditions. Keep your fish tank at a comfortable stocking level.


Are Worms In A Fish Tank Bad?

Although a little nasty, worms that reside in your substrate or water column are not a major concern. But any form of worm that lives on or in your fish is a parasite that must be removed right away. Your fish may actually lose all of their life at their hands. Dealing with them sooner rather than later is preferable.

Are Fish Tank Worms Harmful To Humans?

Anisakiasis is a disease that is brought on in humans by fish roundworms. The symptoms of this infection include abdominal pain, nausea, vomiting, abdominal distention, diarrhea, blood and mucus in the stool, and slight fever, according to the Centers for Disease Control in the USA.

Where Do Worms In Fish Tank Come From?

Worms in a fish tank might have come with a new fish or plant, or they might have been in the gravel from another tank that was moved into the tank. Quite often, worms are not seen entering your tank.

Are Planaria Worms Harmful To Fish?

Planaria are usually not a big problem if you only keep fish. Some fish, like Bettas and Plecos, are even said to eat them! Planaria might not hurt fish, but if you keep shrimp, it might be more of a problem.


Worms can enter fish tanks in a number of ways, but they are most often introduced through new plants or fish. Worms can be harmful to fish, but they are not typically harmful to humans. It is important to keep your tank clean and free of debris to prevent worms from infesting it. You can also use a dewormer to prevent worms from getting into your tank. If you do find worms in your tank, be sure to remove them as soon as possible.

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