General

Other parasites that cause clinical disease in rainbowfishes can be encysted in various tissues or reside in the gastrointestinal tract or other organs (e.g., gallbladder). These parasites include various species of cestodes, nematodes, acanthocephalans, and coccidia. They include harmless freeliving types, roundworms, tapeworms, and trematodes. However, others have larval stages that live in lymph ducts and blood vessels, and they are difficult to treat without dangerous side effects. Most worms do not pose a serious health risk to rainbowfishes because they often have complicated life cycles in which the fish may serve as only one of possibly several intermediate hosts. Rainbowfishes with internal worms may appear completely healthy, exhibiting no symptoms of infestation.

Many parasitic infections of fish are treated with medicated baths (e.g., formalin, praziquantel, metronidazole, etc.) or altered salinity. Copper sulphate is very effective for treatment of some parasitic infections. Lufenuron baths have been used to control crustacean parasites. Intestinal parasites are readily removed with various drug treatments. Gastrointestinal parasites may be treated by incorporating medication in a gel food form, but only if the animal is eating. Gel food can be homemade and is useful for administering common antiparasitic drugs (e.g., fenbendazole, metronidazole, praziquantel, pyrantel pamoate). These drugs can also be given via gastric irrigation using an appropriate-sized rubber catheter. Ivermectin should be avoided because it can cause neurologic signs and death in fish at therapeutic doses.

Although specific therapeutic options vary for each organism, chemical treatment is of temporary value if water quality and management are poor. Aquarium conditions should be improved first.