Diseases of Freshwater Fish

Popular species of freshwater fish for home aquariums include goldfish, tropical fish and freshwater cichlids. All of these fish are prone to some general fish diseases. Healthy fish tank water is not pure water, but includes microscopic bacteria, fungi and zooplankton. Healthy fish live in harmony with these microscopic organisms. When fish are highly stressed or forced to swim in poor water conditions, this bacteria can promote diseases.

  1. Ick or White Spot

    • "Ick" or "white spot" are the common names for Ichthyophthirius multifilis, a microscopic protozoan normally found in freshwater with fish living in it. Fish suffering from ick infection grow white spots all over their bodies. These white spots are the protozoans massing on the fish's body, eating it. Unfortunately, they are not vulnerable to treatment until after these spots start to fall off of the fish, according to "Freshwater Aquarium Problem Solver." The tank's temperature should be raised to 80 degrees F for four days. This kills the ick, but not the fish. All of this time, half of the water in the tank should be changed at least once a day and the gravel cleaned. This raises the water quality, but also helps to remove some floating protozoans.

    Velvet or Gold Dust Disease

    • This is a parasitic infection that causes similar symptoms to ick. Instead of prominent white spots, the fish develops pale grey, silver or gold spots that often appear to be made out of velvet. The fish may breathe much faster than usual and may scrape its body along gravel, plants or decorations trying to soothe itchiness. Treatment is similar to ick, except that 1 tablespoon of aquarium salt can be added for each 5 gallons of water in the tank. Malachite green formulated for aquariums also helps to kill the parasites, according to "Freshwater Aquariums For Dummies."

    Pop Eye

    • This bacterial disease gets its name from the characteristic bulging eyes of afflicted fish. The eyes may also seem to have milky clouds across them. This can be caused by either parasites or poor water conditions. Do a partial water change and do water tests to see if ammonia, chlorine or the pH is out of balance. Otherwise, treat for velvet with the exclusion of malachite green, according to "Freshwater Aquariums For Dummies."

    Fungal Growths

    • These often appear to be lumps of cotton stuck to the fish. Despite the common name of "fungal growths," the cause is a bacterial disease, according to "Freshwater Aquarium Problem Solver." Create a medicinal bath for the fish. Add aquarium salt to a clean, unused bucket or small aquarium using the same amounts as for velvet. Add fresh water that is ideally the same temperature as the tank. Place the fish in the bath for 60 seconds per 24 hours until the growths have disappeared.