Camallanus Red Worms – Symptoms, Prevention, & Easy Treatments

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Camallanus Red Worms are highly infectious parasites that live in the intestines of infected fish.

These tiny red worms anchor themselves in the fish’s intestinal tract and the only sign a fish is infected is usually a collection of tiny red worms protruding from the fish’s anus.

What are Camallanus Red Worms?

Camallanus Red Worms (Camallanus Cotti) are highly contagious parasitic nematodes that are extremely common in the freshwater fishkeeping hobby.

These tiny little worms live their lives in the fish’s intestinal tract where they anchor themselves, feasting on the fish’s blood. Often, the only sign a fish is infected with Camallanus Red Worms is the collection of tiny worms protruding from the fish’s anus.

Camallanus Red Worms are highly infectious and quickly spread through a tank of fish. They are most often associated with livebearers, especially those livebearers that are renowned for eating anything they find on the aquarium substrate, such as guppies and mollies.

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How Do Camallanus Red Worm Infect Fish

Camallanus Red Worms reproduce by producing live offspring. Female Camallanus Red Worms incubate their eggs inside their bodies, which hatch into live larvae. These larvae are then passed out of the host fish in the fish’s feces.

Typically these larvae are then ingested by other fish, after which the cycle starts all over again.

Camallanus Cotti doesn’t require an intermediate host between the adult nematodes living in the infected fish and the next generation. Other species of Camallanus that are also frequently present in our aquarium do require an intermediate host, often these hosts are crustaceans such as copepods.

When fish eat either the live larvae or crustaceans that are infected with Camallanus, the Camallanus Worms quickly take hold inside the fish’s intestinal tract.

How Does Camallanus Red Worm Get Into Our Aquariums?

The most common way we find our fish infected with Camallanus Red Worms is after we have introduced new fish to our tanks. These new additions have brought the parasite in with them and quickly passed live larvae with their feces.

Alternatively, one of the species of Camallanus that utilizes an intermediate host can be introduced through the feeding of live foods such a cyclops.

How To Detect Camallanus Red Worm In The Aquarium?

One of the biggest problems with Camallanus Red Worm is that it can be very difficult to detect an infestation in the early stages. Unfortunately, Camallanus spread extremely quickly through a tank, and by the time you realize you have a problem, your fish could be heavily infested.

The symptoms you should look out for include;

  • Bloating of the abdomen
  • Lack of interest in food
  • Red worms protruding from the anus
  • Large numbers of fish dying over a short period

In my experience, sitting observing the fish in your aquarium is the best way to spot the symptoms of Camallanus Red Worms.

Treating Fish Infected With Camallanus Red Worm

Camallanus Red Worm is notoriously difficult to treat. There are currently two main chemicals that are known to treat Camallanus. These are Fenbendazole and Levamisole.

In my experience, Levamisole is more effective and easier to use than Fenbendazole.

Treating Camallanus Worms with Levamisole

Levamisole targets the neurotransmitters in the worms and paralyzes them, allowing the fish to pass them naturally when they go to the bathroom. The Levamisole is absorbed by the gut and passed onto the Camallanus Worm when they feed to the fish’s intestines.

It is possible to source Levamisole as a stand-alone product, and then mix it with water and add it to your aquarium. In reality, this is a risky tactic and you can easily overdose your tank.

The best treatment I have found for Camallanus Red Worm is Expel-P which is made by Fritz. To treat an aquarium with Expel-P, use the following instructions;

  1. Use 1 packet of Expel-P for every 10 gallons (38 liters) of water
  2. After 24 hours, perform a 25% water change, removing as many excreted worms from the substrate as possible by gravel vacuuming.
  3. Repeat weekly as necessary to erradicate all Camallanus Worms

Fritz gives a number of recommendations when using Expel-P to make the treatment as effective as possible.

  • For best results, treat fish in a barebottom quaranteine tank
  • Remove carbon or chemical filtration from filters as they may pull Expel-P from the water
  • Switch off UV Sterilizers
  • Turn off aquarium lights for 24 hours as the active ingredient is light sensative
  • Expel-P is safe for use with shrimps and snails

Excel-P also doesn’t color the water or affect the ‘good’ bacteria we utilize in our aquarium filters.

Treating with Levamisole in Europe

At the time of writing, Expel-P is not available in Europe. So if you do not have access to Expel-P, try eSHa -ndx. The active ingredient in eSHa -ndx is also Levamisole.

eSHA -ndx works against parasitic nematodes like Camallanus, Capillaria, Pseudo-capillaria, Eustrongylides, Oxyuris and other roundworms.

eSHa -ndx can be used to treat freshwater and marine fish. It also doesn’t affect aquarium plants or the beneficial bacteria that live in aquarium filters.

Treating Camallanus Worms with Fenbendazole

Fenbendazole is a very effective treatment for Camallanus Worms, however, there is a good chance it will have a negative effect on other inhabitants of the aquarium.

Fenbendazole doesn’t actually kill the Camallanus Worms, instead, it slowly expels them from the fish’s body. This is a positive way to clear the fish of Camallanus Worms. If a fish were to be heavily infested with worms, and Fenbendazole was to kill those worms, there is a good chance the worms would rot inside the fish, causing further issues.

Fenbendazole is sourced as a powder, usually from animal feed stores. The recommended way to feed it to your fish is by mixing it with their food. As with Levamisole, the substrate should be regularly vacuumed during treatment to remove any live worms or larvae.

I have never had much success using Fenbendazole, and given that Levamisole is so simple to use, I would always recommend using Expel-P or eSHa -ndx.

What to do After Treating for Camallanus Red Worm?

24 hours after treating your fish for Camallanus Red Worm you should thoroughly vacuum your aquarium substrate.

It is perfectly feasible that some of the Camallanus worms, or their lavare, will survive the treatment process, and as such it is important to remove them from the aquarium as soon as possible.

The best way to remove any parasites that reside in the aquarium substrate is by gravel vacuuming.

It is also advisable to thoroughly clean any nets or other equipment that may have entered the infected aquarium. Camallanus Red Worm larvae can be present in a single droplet of water, meaning any item that has been in the infected aquarium should be totally disinfected before placing it in another tank.

One of the reasons Camallanus Red Worm spreads from one tank to another so quickly is that a single net used in multiple aquariums can infect an entire fish room.

Placing all equipment and decorations in a bucket containing a bleach solution will kill any Camallanus larvae. Items should then be thoroughly rinsed before using in a fish tank again.

Can Camallanus Red Worms Kill Your Fish?

Simple answer, yes!

When the number of Camallanus Red Worms in an individual fish swell, the fish will quickly die. The Camallanus Worms drain the fish, which firstly loses interest in food, then takes on a bloated abdomen before quickly dying.

In the wild, there is a good chance fish will live with Camallanus Red Worms, and other internal parasites in their systems. They survive because they usually only have a small number of parasites in their systems.

In the closed environments that are our aquariums, each fish ends up suffering from a much higher infestation of parasites than their wild cousins, and it is this higher concentration of parasites that quickly leads to the demise of our fish.

How do Camallanus Red Worms Reproduce?

The way the Camallanus Worm reproduces varies depending on which species it is.

Camallanus Cotti Life Cycle

Camallanus cotti is the only known species of Camallanus worm that do not require an intermediate host to complete their life cycle.

Mature female Camallanus cotti give birth to live, first stage large that are excreted from the host fish when the fish goes to the bathroom. These larvae are capable of infecting other fish directly.

After being excreted from the host fish, the larvae sink to the substrate where they wait to be consumed by another fish feeding from the bottom of the tank. It is because this species of Camallanus does not require an intermediate host that it is the most prevalent form in our aquariums.

Other Species of Camallanus Worms

All the other known species of Camallanus Worms require an intermediate host to complete their life cycle.

The female Camllanus gives birth to first-stage larvae, which are excreted when the host fish goes to the bathroom. These larvae are then consumed by small crustaceans such as Gammarus or Cyclops.

Once the larvae are inside the crustacean they will molt a couple of times, becoming third-stage larvae before going into a kind of suspended animation whilst they wait for the crustacean to be consumed by a fish.

Once the larvae sense the crustacean has been consumed by a fish it comes back to life and begins feeding on the new host fish. After a short period, the whole cycle starts over again.

How to Prevent Camallanus Red Worms Entering an Aquarium?

When it comes to preventing Camallanus Red Worms from entering your aquarium in the first place, the best weapon in your arsenal is quarantining new fish. I can not recommend quarantining new fish highly enough!

Quarantining new fish simply means keeping any new fish you get in a separate aquarium from your main tank until you have a chance to assess if they are carrying any pests or diseases and treating them accordingly.

I always quarantine my new fish for at least 2 weeks prior to adding them to tanks in my fish room. I also treat new fish for pests and diseases as a precaution.

Are Camallanus Red Worms Harmful to Shrimps or Snails?

No, Camallanus Red Worms don’t pose any issues for shrimps or snails. To complete their life cycles Cmallanus Red Worms need a host fish.

Are Camallanus Red Worms Harmful to People?

No, Camallanus Red Worms do not pose any issues to humans. With that said, I strongly recommend practicing good hand hygiene when handling fish or any medications you are using with your fish.


Camallanus Red Worms can devastate a tank of fish. They are highly contagious and can spread from tank to tank, even if the fish themselves don’t move from tank to tank.

If you identify you have Camallanus Red Worms, order an appropriate medication and start treating ASAP.

About the Author

I’ve been keeping, breeding, and showing tropical fish for nearly 30 years. Over that time I’ve done it all! I’ve had great success and I’ve made some really foolish mistakes (like the time I bought an Asain Walking Catfish). Read more…
Richard James

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