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Treating Worms in Fish Aquariums

Treating Worms in Fish Aquariums

At some point in their lives, many fish will suffer from the unfortunate effects of worms in their aquatic environment. Parasites and worms can be very hard to pinpoint, but there are steps you can take to treat and prevent these pesky parasites from bothering your fish.

Common Worms in Fish

Nematodes, also known as hookworms and roundworms, are one of the largest groups of worms. This group of worms contains a variety of internal parasites that live in the digestive systems of fish. The main problem species are Cammalanus and Capillaria. Diagnosing these worms can be difficult as they are often found in the gastrointestinal tract post-mortem. 

Symptoms of Capillaria worms include weight loss, intestinal blockage, and even death. One of the first and most evident symptoms of Cammalanus worms is the presence of a red-colored worm protruding from the anal vent of an infected fish. Other symptoms include weight loss and being more susceptible to other diseases.

Cestodes, also known as tapeworms, are also difficult to diagnose. Common symptoms include failure to thrive or gain weight. Diagnosis is usually done by examining a fresh fecal sample under a microscope.

Trematodes, commonly referred to as flukes, are microscopic and can cause irritation to the skin, eyes, and gills. A majority of systems have a small number of flukes, but they aren’t always an issue. Flukes start to multiply and become a problem when fish become stressed. Symptoms include red, irritated skin and flashing behavior (rubbing against tank walls or other objects).

Treating Parasitic Worms in Fish

Before you start treating parasitic worms in your fish, it’s best to consult your veterinarian for the correct diagnosis and a proper treatment plan. If treated incorrectly, parasites can become resistant to certain medications, making treatment even more difficult. Common treatment plans include administering a fish dewormer that contains active ingredients such as fenbendazole or praziquantel.

Fenbendazole will kill a wide range of internal worms by interrupting the parasites’ cellular transport and metabolism. Fish Bendazole from Thomas Labs® contains fenbendazole and is designed to remove worms and other parasites from fresh and saltwater aquariums and from within the fish themselves. It is effective against common organisms such as Planaria, Camallanus, and Aiptasia anemones. Plus, it is one of the fastest and most effective agents against aquatic parasites and other dangerous rogue organisms.

Praziquantel works by paralyzing the parasite and allowing the host to more easily shed the parasite. Fish Tapes and Fish Tapes Forte are safe and effective worming agents that contain praziquantel. They are designed for the removal and prevention of flatworms and parasites from within aquatic environments and from within the fish themselves. Plus, they work to prevent parasites from infesting your fish again.

Preventing Parasitic Worms in Fish

Prevention is key when it comes to dealing with parasitic organisms. For this reason, it’s important to properly quarantine all new fish, as well as any sick or injured fish. Having the new fish in a completely separate system for at least 4 to 6 weeks will allow you to observe any disease and help prevent the spread of potential parasites.

Practicing good hygiene within your aquarium will also help. This includes removing feces and organic debris as often as possible. It’s also important to be careful when giving live feed to your fish. Some species of worms, like Cammalanus, require a copepod or similar crustacean for the transmission of the parasite. Therefore, introducing those crustaceans into your aquarium opens up the possibility of introducing parasites as well.

Deworming fish can be a long and frustrating process. Quarantining new fish, practicing good aquarium hygiene, and properly using a fish dewormer when needed will help ensure healthy fish!


The materials and information provided on this website are not intended to replace the medical advice or services of your veterinarian or other pet healthcare professional. Consult your own veterinarian if you have medical questions concerning diagnosis, treatment, therapy, or medical attention.

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