Home » Aquarium Guides » Easy Methods To Get Rid of Red Worms (Camallanus / Capillria Worm)

Easy Methods To Get Rid of Red Worms (Camallanus / Capillria Worm)

Red worms (camallanus/capillria worms) are parasitic worms that you commonly find on aquarium fish.

They have the potential to infect fish species and could cause greater damage to your aquarium.

These tiny little creatures could fit in between gravel and sand very easily. As such, we cannot spot them at once.

How red worms look like?

red worm

There are two types of red worms that affect fish in aquariums; Camallanus and Capillria. Both species are parasites that host inside fish.


Camallanus, (also known as red worms) is a tiny roundworm that infects a range of freshwater fish. 

These worms are an intestinal parasite that feeds on fish blood. They were mostly seen inside tropical fish.

Red worms will come in different sizes according to their age and type of the species. Some large worms may grow up to 2mm long.

They look like thin, red threads.

These worms infect both wild and aquarium fish. The fish becomes a host for the parasite when they ingest infected crustaceans. 

Once the red worm gets inside of the fish, they will drill in with rasping organs found on the nematode anterior. After the drilling, the worm anchor itself to the fish.

Adult worms usually get their reddish color by feeding blood from the fish.


Capillria is another type of nematode, which is very similar to camallanus worms.

These parasites produce the same symptoms as the camallanus worm, but the only difference is that they will stick out from the anus of the fish.

This parasite will infect almost any breed of fish. But cichlids, guppies, and livebearers are the hardest to hit. 

By chance, if you notice that these fish are rapidly dying in your tank, the main suspect will be this parasite. You can find these worms producing in dull and cloudy water. 

They are very rare to see in a well-maintained aquarium setup.

Are red worms harmful or useful?

Red worms are harmful to fish. When these red worms have invaded a fish tank, it would be very difficult to even identify them.

You cannot even spot them. If we take juvenile fish for example, once they are infected by these red worms, that will cause them to have slower growth.

On the other hand, the grown-up fish would find it difficult to reproduce.

Moreover, the red worms would cause external limps, cysts as well. Not only that but also, it makes the fish lose interest in consuming their food .

Once they attack on a much severe level, the fish would tend to lose their weight and their skin tissues would die. These red worms could lead to internal bleeding.

Apart from that, there would be severe repercussions such as irritated digestive tracts and bacterial infections.

How to detect red worms in the aquarium


Detecting these parasites is tough. These red worms may not be visible at most times. Younger fish in your tank will die at slower growth rates. 

Additionally, adult fish in the tank may experience difficulty reproducing, bloating, external lumps, and cysts. Loss of interest in food, rapid weight losses, or dying skin tissue can signify severe parasitic infestation.

The red worm can infect even the best-maintained fish without even showing any symptoms.

Unclean environments such as overcrowding, poor diet, and poor water quality will lower the fish’s immune system. 

When the fish has low immunity, it is easier for the worm to infect and cause damage. Below are some symptoms in a detailed form. 

  1. Wasting.

If you find your fish overweighted or has a hollow stomach, it can be because of nematode multiplication inside the body.

  1. Bloating 

A distended stomach of fish can also be a sign of parasite infections.

  1. Low Appetite

If the fish is not eating as they used to eat, this can be another sign.

  1. Swimming in Place 

If the fish is shaking or simply swimming in place, this is a sign that the infection has become worse.


These parasites produce eggs instead of living larvae, as the camallanus worm does. To see which type of nematodes has infected your fish, you must use a microscope. 

If capillaria worm has infected the fish, You will notice symptoms like barrel-shaped eggs in the feces.

A well-maintained aquarium also will have some small numbers of nematodes. It is not noticeable to see light nematode infections where isolation is not a must. 

But in the case of the poorly maintained tank, the chances of multiplying these parasites are high, which will lead to serious harm or may even kill your aquatic life.

How to get rid of red worms in a fish tank 

Figuring out how to remove these parasites from your tanks can be very stressful. But if you follow the below-mentioned steps, You will be able to stop an infection.

The first thing you have to do after noticing your aquarium has these parasites is treating your fish. 

Fish Treatment

Drugs such as flubendazole, levamisole, mebendazole, trichlorfon and triclabendazole can be used to treat nemetodes in fish.

However, non of these drugs are proven to be effective on every fish type. The type of medication will change according to the fish species.

Medication has to be mixed with the food at a 1 to 5 ratio. Fish should eat the medicine. Hence, we mix the drug with the food. Medicated food is not difficult for the fish to consume.

You can follow these steps

  1. Heat a quarter cup of water in a microwave for about five minutes.
  2. Then mix a quarter ounce of medication in hot water and mix well.
  3. You must add two tablespoons of commercial fish food, flake, or pellets when heating the water.
  4. Stir well the mixture till it becomes a paste-like consistency.
  5. Mix the paste well and spread it out into a pancake, and refrigerate it for the fish.
  6. You must feed this medicated mixture to the fish for about a month. You might notice that the fish will sometimes not eat the medicated food like regular fish food, so you have to leave the food in the aquarium.

Always keep in mind that the red worms or any other parasite will get affected well when eaten.

Adding the medication to the water is not that effective.

Some medicine has instructed to directly give it to the fish by adding it to the water, which is a false statement and must not do. This medication has large molecules, which is hard for the fish gills or skin to absorb through the water.

Aquarium Treatment 

Once treating the fish is done, you must now turn your attention toward the fish tank.

  1. You must initially add 2mg levamisole or any other recommended medication per liter to treat the tank.
  2. If you have 50 liters, add around 100mg in one tank.
  3. Then leave this solution for about 24 hours 
  4. After that, you must do a 70 to 100% water change in your tank. Finally, make sure that you vacuum the gravel well.
  5. Vacuuming is essential because these medications will only paralyze the parasite instead of killing them. So make sure to suck them out using a gravel vacuum.

This treatment has to be followed repeatedly for two weeks.


It’s always better to feed your fish after each treatment. This feeding will help the fish’s digestive system expel the dead worms on time, which will avoid them stressing out.

Once the worm is dead, you can feed your fish with any suitable commercial fish food.

Ensure to keep a close look at the fish for any signs of stress so that you can take appropriate actions accordingly. 

Sadly, even after the treatment, if your fish shows signs of bloating or overweight, your fish is not curable. These are signs of infection. 

If the fish is not expelling any worms, it has them inside the body.

The worms will eventually decay. It will again cause a secondary infection, which can be contagious, and you must avoid infecting other fish in your tank.

You must isolate the infected fish in a separate tank till it passes away. 

How to prevent in having red worms in your fish tank

It is always better to act wisely and avoid any potential attack of red worms rather than treating them once you encounter them.

To prevent that, you could quarantine the new fish you purchase before adding them to the fish tank.

In addition to that, make sure that you do not provide too much food for  the fish.

Further ensure that you vacuum the tank floor on a regular basis. Always use a healthy and an efficient filter. More importantly, make sure that you use crucial chemicals to maintain the water quality.

Check before buy your fish

Obviously, encountering these irritating little creatures in your beautiful fish tank would be a messy experience.

They could make the tank look unpleasant and it could even help to deteriorate the health of the fish too.

As such it is quite vital that you check the fish carefully and see whether there are any early signs of such worm infestations.

That will avoid making any future disturbance and if you spot any you need to treat them in advance and then proceed with the rest.

Related : Treat Horsehair Worm in Ghost Shrimp | 2 Ways Full Guide

Quarantine before putting your fish in tank

This is somewhat a debatable topic to discuss as you could have different thoughts and views on this.

Consider that you are purchasing the fish from the same aquatic shop, then it is obvious that all those fish are sharing the same micro ecological conditions such as bacterial elements and microscopic fauna.

As such, you could ignore this, if you are confident that you are purchasing healthy and hardy fish.

As such you just add them to the fish tank without proceeding with quarantining them.

Having said that, consider that you are obtaining them from different sources such as from other retailers, other hobbyists’ tanks or even online, you are encouraged to quarantine them.

It would make sure that your fish tank would continue to be healthy and safe too.

Consider that if you wish to add gentler fish species which are vulnerable for diseases, you need to quarantine them for a certain period despite you buying them from a regular store. 

Finally, let us say that if you have a tank which did not have any livestock for a prolonged time, in that circumstance, quarantine would be a wise choice.

Related questions 

How do you get rid of fish worms?

The best way to get rid of these worms is by having clean water and mid-temperature water in your tank. 

If your fish gets infected by chance, first, you have to treat your fish in the tank separately using recommended medication. 

You can prepare the medication solution by mixing it with the fish food. You should feed this medication rather than adding the mediational solution directly into the water. 

After that, you must treat your tank. First, add 2mg levamisole or any other recommended medication per liter. Keep the solution for about 24 hours. 

Then do a 70 or 100% water change and make sure to vacuum the gravel well when doing that. Because the medication will paralyze the worms and not kill them, you must clear them off the tank before adding the fish again.

Red worms in aquarium substrate

These worms will live in dirty water. Usually, Red worms are parasitic roundworm that uses a fish as its host. 

Are camallanus and capillaria worms dangerous to shrimp and snails?

No, these worms are affected mainly by freshwater fish and not by snails and shrimp.

Are Camallanus worms dangerous to a human?

No, this parasite is not a danger to humans.

Are Capillaria worms dangerous to a human?

Caprllaria hepatica is very rare to see in a human. There are no endemic areas of infection with these parasites. 

Human infection primarily results from Zoonotic transmission. Once infected, humans will have diarrhea and emaciation. However, only about 40 cases of Capillaria infection in humans were reported.


Nematode worms are the most commonly seen pathogen in a tank, and these parasites infect a range of aquatic animals, mainly freshwater fish. 

Keep in mind that your tank’s water has to be cleaned and kept at a required temperature for the fish to thrive without these parasites. 

Too much warm water can deplete oxygen and increase the risk of nematode infection. Taking required measures while buying new fish and avoiding feeding them with live food can reduce the risk of these parasite infestations.

Read Next : Do Neon Tetras Eat Plants? | 8 essential facts on Neon Tetra Feeding |

Sharing is caring!

About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.