Ichthyophthirius multifiliis
Parasitic species of protozoan / From Wikipedia, the free encyclopedia
Ichthyophthirius multifiliis, also called "white spot disease", "ick" or "ich" is a disease that causes little white spots on fresh water fish. It is one of the most common parasites of fish. It often affects pet fish in tanks and ponds, as well as farm-raised food fish species. Wild fish populations can also get the parasite.