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The camallanus worm is a common intestinal parasite in tropical fish. It feeds on the blood of fish by drilling via a rasping organ positioned at the anterior end of the nematode.

The organ also provides anchorage. The worm’s posterior is commonly observed dangling from the anus of the affected fish. It will turn red as it draws blood from the fish.

How to Treat Fish for Camallanus Worms?

How to Treat Fish for Camallanus Worms?

Most aquarists associate the fish with livebearing fish, but they will affect any fish they come across. The species of the worm has been recorded in varying and diverse hosts from across the world.

Information about the worm seems to be mostly traded in aquarium-focused forums, and it can sometimes be conflicting and limited. Read on for the pathology, treatment, and prevention of this notorious parasite.

How does Camallanus Worm Get into Fish Tank?

How does Camallanus Worm Get into Fish Tank?

How does Camallanus Worm Get into Fish Tank?

The various species of Camallanus Worms target various freshwater fish in the wild. In aquariums, however, the worms can live in such intermediate hosts like Gammarus and crustaceans. It is also suspected that the worm can be introduced in aquaria via live foods and live plants. Copepods are common hosts of the worms, and they are sold as live foods.

Cross-contamination is also a contributing factor, especially where the same equipment is used for several tanks.

Detection is not always easy in new fish. Even if you quarantine newly-acquired fish, the worms can hide in its gut, especially if the worms are only a few.

Can Camallanus Kill your Fish?

Can Camallanus Kill your Fish?

Can Camallanus Kill your Fish?

Camallanus worms will kill fish in severe infestations. It can trigger several consecutive deaths, often with no clear cause. Common symptoms of infestation include wasting, abdominal bloating, and disinterest in food. Look out for a starved appearance.

Livebearers can exhibit shivers and shakes, and they can appear as if they are swimming in place. If your fish is mainly active and you observe them remaining in one place for a while, they may be infested with the worms.

Such symptoms can be nonexistent in fish kept under stable conditions. The infestation will, however, be made worse by poor water quality, overcrowding, and an unsuitable diet. These factors will weaken the immunity of the host fish and cause the infestation to be worse.

How Do Camallanus Worms Reproduce?

How Do Camallanus Worms Reproduce?

How Do Camallanus Worms Reproduce?

Camallanus worms have three primary stages in their life cycles.

Mature females produce a sizeable population of first-stage larvae. The larvae seek habitat in the substrate where they are consumed by small crustaceans, after which they proceed to the gut of the host. While in the gut, the larvae feed and grow. The most common intermediate hosts include the Gammarus and Cyclops.

The larvae will molt two times in about a week, and third-stage larvae will be formed to sit inactive in the host. If the crustacean is eaten by fish, these larvae will become active and resume feeding. It will only need to molt two more times to form adult males or females. The adult worms are what are commonly seen extending from the anus of the fish.

Most of the known Camallanus worms will rely on an intermediate host to finish the life cycle. The Camallanus Cotti, however, does not need an intermediate host, as the first stage larvae from the mature females can infect other fish directly. This species is credited with the most aquarium infestations. It will target a range of fish in aquaria, including labyrinth fish, rainbowfish, and cichlid fish.

Are Camallanus Worms Dangerous to Shrimp and Snails?

Camallanus worms will mostly affect fish in an aquarium and not snails, shrimps, or other inhabitants.

Are Camallanus Worms Dangerous to Humans?

The common intermediate hosts of camallanus worms are crustaceans. They do not appear to be dangerous to humans. Treating Your Fish for Camallanus Worms

There are several medication ways to address an infestation of camallanus worms. These options include levamisole and fenbendazole. Most medication is designed to paralyze the worms, after which they are forced out of the gut of the infected fish and into the tank. The substrate should be cleaned, and the water changed.

The medication can be used as follows:

Camallanus Worms and Fenbendazole

Fenbendazole is an effective treatment for camallanus worms. It might, however, kill other inhabitants of your tank, so it is best to prepare a fish-food with it. Instead of instantly killing the worms, fenbendazole works by slowly expelling them out of the fish. If a large number of the parasite infects your fish, it would not be suitable to kill all of them as they would begin rotting in your pet’s gut.

You can source for the fenbendazole packets in animal health stores. Ensure that you thoroughly mix the powder with the food, that is mix until you cannot see any chunks of the medication in the food. You can use a blender for improved efficiency.

The fish will start releasing the camallanus worms a few days after consuming the medicated food. The treatment can be given once a week for two or three weeks. Clean the aquarium and remove the debris since fenbendazole will not target the larvae in the dead worms. The free-living larvae can also survive for three weeks without a host.

Camallanus Worms and Levamisole

Levamisole is an anti-worm agent, and it is especially popular in the treatment of large livestock like cattle. Its efficiency is also favored by aquatic enthusiasts, although information concerning its use and usefulness is not very clear.

Levamisole is absorbed into the gut, and it targets the neurotransmitters of the camallanus worm to paralyze it. The fish will then pass these inactive parasites. To extract these worms, it is advisable to vacuum the gravel thoroughly.

The LD-50 of the medication is 250mg/l per 24 hours. Overdosing the treatment could result in the death of your pets.

The medication is quickly absorbed into the animal’s digestive system. Only a small amount is excreted unused in the waste of the fish. 70% of the treatment will be expelled by the fish within three days, and it can be removed by changing the water or including activated charcoal in the aquarium’s filtration system.

You can follow the treatment plan below when using levamisole

  1. Figure out the appropriate dosage. A dose equivalent to 2 ppm is commonly recommended for levamisole-based medications. Adding extra will only cause strain in your fish instead of treating them.
  2. Add the dosage and evaluate the pets after four hours. The best time to dose the aquarium is when you will be around so that you constantly monitor the fish. Most of the camallanus worms will be released in the first 24 hours after medication. Since doing a water change too soon will remove the medication, you can vacuum any of the worms that you see at the bottom. If you leave them for too long, they will become food, and the cycle will start all over again.

If the pets are eating, provide them with food that is high in protein to help them expel the worms.

  1. A water change is best done on the third day. It takes three days for levamisole to be absorbed by the aquatic pets, and any unused medication will be excreted by the fish at this time. A 30% water change will be fine to avoid stressing the fish.
  2. Repeat the previous steps after two weeks. Repeating the process will get rid of the eggs that might have hatched. You can do another treatment after another two weeks to ensure that your system is free from any worms or eggs.

This treatment is largely effective if the fish are not severely infected. Most of the pets will survive the medication and regain their health, but some may suffer intense damage in their digestive system. It is commonly thought that levamisole only works when the PH is below 7. It has, however, been shown to be stable in both low and high PH levels.

Antihelminthic treatments are typically dangerous for shrimp and snails, and it is thus best to remove them before dosing your tank. When dealing with delicate or expensive fish, it is best to seek guidance from a veterinarian.


Camallanus worms are common internal parasites in aquaria. They target many fish species, including goldfish, mollies, angelfish, and guppies. It is challenging to deal with these worms because light infestations are hard to detect. It is not until adult worms are seen hanging from the anus of a fish that most aquarists will be sure of an infestation.

These worms feed on the blood of the fish, resulting in a starved appearance in the pets. If you observe your pet thinning away, it could be a sign of the worms. Such symptoms can, however, be missing in fish kept in stable and good water conditions.

Treatment will require the inclusion of medications, with the most common ones being levamisole and fenbendazole.

To prevent an infestation by camallanus worms, it is good practice to quarantine any newly-acquired fish. The worms target crustaceans as their hosts, and they can find their way into your aquarium through live foods consisting of crustaceans. If you must feed crustaceans, ensure they are sourced from ponds without fish.

Written by Fabian

Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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