How to Treat Camallanus Red Worms in Aquarium Fish

Fish diseases can be notoriously hard to diagnose, but one of the more easily recognizable illnesses is an internal parasite called the camallanus red worm. Multiple species of roundworms and nematodes that belong to the Camallanus genus can infect aquarium fish. They attach to the intestinal walls, and they can co-exist for long periods of time with their host. However, added stress factors like bad water quality or tank aggression may weaken the immune system, allowing the worms to cause serious damage and even mortality.

Does My Fish Have Red Worms?

For a while, the fish will look quite normal in the beginning stages of the disease. You may notice that the juvenile fish grow slower than normal, the adults are not breeding as often, and eventually, you will lose a few fish every month. A loss of appetite was also reported by hobbyists.

The telltale sign of this sickness is when you see one or more small, red worms coming out of the fish’s anal vent. It may look like a small cluster of scarlet threads that extend about 1/4 to 1/2 inch (6.6-3.3 cm). The disease has reached a very advanced stage and the fish might appear abnormally thin or swollen from the worms. Secondary infections can develop from worms blocking the intestinal tract.

Camallanus worms can be more easily seen in small livebearers, such as guppies. It only takes a few larvae to cause serious damage in a tiny fish. The worms need a much longer time to multiply to a point where the population that is large enough to take down bigger fish like angelfish.

Guppy with camallanus worm protruding from the anal vent

What causes Camallanus red Worms?

Infected fish can be introduced to an aquarium and the larvae of worms are passed on to the fish. These larvae are then eaten by small crustaceans such as cyclops. A healthy fish can eat infected crustaceans. This causes the larvae to mature and become adults, which allows the cycle to continue. Some species of camallanus worms do not need an intermediate host, and fish can get infected directly by nibbling on fish feces that contain larvae. Cross contamination can also occur when plants, gravel, and equipment are added to infected tanks.

How Do I Get Rid of Camallanus Worms?

Fritz Expel P, which contains levamsole and targets roundworms like camallanus, is a good dewormer. The medication paralyzes adult worms and allows them to be expelled by an aquarium siphon. Follow the manufacturer’s instructions on the box by using 1 packet of Expel-P per 10 gallons (38 L) of water. After 24 hours, perform a 25% water change to remove the excreted parasites. Since levamisole does not affect unhatched eggs, wait two weeks after the initial treatment and then dose the tank again with Expel-P to deal with any remaining worms.

Fritz Expel–P medication for parasitic disease

Some articles suggest putting the dewormer inside food and giving it to the fish. We prefer to treat the entire tank, as sometimes fish lose appetites and you don’t have control over how much medication each fish consumes. You can also use broad-spectrum antifungal or antibiotics if you fish have secondary infections.

The key to recovery is not medication. It’s about lowering stress levels in the aquarium and hospital tanks. To help the worms get rid of their toxins faster and gain weight, feed them high-quality food. Keep the water quality high and vacuum the substrate more frequently to remove any paralyzed parasites. To stop disease spread, disinfect any siphons and nets.

Dosing a packet of Expel-P

How Do I Prevent Camallanus Worms?

All new fish should be quarantined for at least a week to monitor their behavior and appetite before being added to your tanks. This will allow you to avoid infecting any of your animals. While the trio of antibiotics can prevent most infections (bacterial, fungal, or parasitic), you should consider using Expel-P to treat specific concerns. Redworms are not a problem for most fish. However, it can cause problems in some species. Make sure to keep the tank clean, provide fresh water and reduce stress. You can avoid cross-contamination by keeping the quarantine tanks in separate areas, washing your hands after touching the tank, and using separate siphons and nets to quarantine fish.

Check out our articles for more information about fish diseases. Learn how to diagnose, treat, and prevent the most common ailments.

Attributions 190729 Guppy 01 by BlueBreezeWiki (CC BY-SA 3.0)