A monogenetic trematode. Several species affect fish. These parasites tear out small pieces of the gills of the fish, causing tremendous damage. Can also be found on the skin, in lesser numbers. Usually when fish are crowded. They have a direct life cycle. Parasite can complete its entire life cycle on a single host.
Treatment is specific and effective. Outlook good if correctly diagnosed. Badly affected fish will seldom recover properly.
Improve water quality, keep bottom of tanks clean, reduce stock density.
Dr. Jacobs, Bruno
Fish Medical sprl