There are several parasitic diseases in fish that freshwater angelfish are prone to. Wild caught angelfish in particular often introduce parasites uncommon to the tank making quarantine imperative when introducing wild caught angelfish to your tank. Beyond introducing wild angels to your tank, common causes of parasitic infections or overload are an unhealthy tank environment, feeding your fish too much, and keeping too many fish in a tank. A healthy aquarium and good angelfish care will prevent many parasites from taking over. If you are having trouble identifying the diseases in your fish, some fish stores may be able to do scrapings, or use other techniques to identify the parasite for treatment.
Hexamita is a genus of protozoa likely found in all angelfish. But it doesn’t usually cause illness unless your angelfish are living in dirty water, overfed, overcrowded, are elderly, or are affected by another disease. Symptoms of Hexamita include white stringy feces, pus filled pores in the head and along the lateral line, lethargy, loss of appetite, and a darkening of color. The white stringy feces are diagnostic of Hexamita and often the first and only symptom. Treat Hexamita in angelfish by raising the water temperature to 95 degrees for about a week to 10 days and using a metronidazole medication such as Seachem Metronidazole. If only one fish appears infected, you can treat that fish in a separate hospital tank. According to Tropical Fishlopaedia, “Some aquarists have reported a better cure rate using metronidazole in conjunction with an antimicrobial (to treat nay concurrent systemic bacterial infection).”
Because Hexamita is prevalent in angelfish, whenever your angelfish are affected by any other disease or parasite, you should also watch for or suspect a Hexamita outbreak as well.
Gill flukes are another parasite common to angelfish. Red and inflamed gills, labored breathing, rubbing on rocks, excessive body slime, and erratic swimming are symptoms of gill flukes, You can treat gill flukes by increasing the water temperature to 95 degrees F for a week to 10 days and using a formalin/malachite green combination treatment.
Capillaria is a roundworm common to many animals, including angelfish fish. Positive diagnosis is done by examining feces under a microscope. In severe cases you may see the worm pass with feces. Symptoms include loss of weight despite eating normally and loss of appetite. You can treat with an anti-parasitic medicated fish food or water treament that contains Levimasole, Piperazine, or Fenbendazole, and frequent partial water changes during treatment as the eggs and worms will be expelled during treatment.
Ich (Ichthyophthirius multifiliis) also known as white spot disease or ick, is a common protozoan parasite. When an angels’ resistance weakens, or water conditions deteriorate, it’s possible for ich to appear. A sudden change in water temperature can also trigger the infection. Ich is characterized by small white spots about the size of a grain of salt on the fish. It covers the whole fish, but is concentrated around the gills.
Raising the water temperature to about 85 to 90 degrees is a good start to rid the fish of the parasite. This will spread up the lifecycle of the ich parasite and also speed up the effectiveness of the treatment.
Change about 20 to 25 percent of the water every four days until your fish are visibly free if the ich white spots. Use a gravel vacuum to stir up the gravel and vacuum out more of the ich cysts in the tank. At the same time, use one of any of the commercial ich products such as QuICK-Cure. These generally contain copper, formalin, machalite green or a combination of these chemicals. Before adding the chemical ich treatment, remove the carbon filter as this will also filter the chemicals needed to treat the ich. As usual, read the instructions and follow them carefully.
Velvet disease, or rust, (Oodinium) will infect freshwater angelfish fish. The parasite looks like rust or velvet and infected fish may spend much of their time trying to rub it off on rocks and other objects in the fish tank. Treatment for velvet disease is the same as for ich. Commercially prepared products made to treat ich will help get rid of this parasite as well.
Flukes, Anchor Worms, Flatworms and Fish Lice
There are many other parasites that can infect angelfish, although less commonly, or that you may see in your fish tank. Some, like flatworms are not usually harmful. Consult with the local fish store for the proper identification and treatment.
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Tropical Fishlopaedia, by Mary Bailey and Peter Burgess, 2000
Freshwater Aquarium for Dummies, by Maddy Hargrove and Mic Hargrove, 2006