Koi can suffer from a variety of diseases, many of which are linked to water quality, stress, or parasites. One of the most common is Ich, or white spot disease, caused by a protozoan parasite that appears as small white dots on the skin and fins. Another frequent issue is fin rot, a bacterial infection that causes the fins to appear frayed or ragged. Ulcers, often resulting from bacterial infections, show up as open sores on the body.
Koi can also be affected by flukes, which are tiny parasitic worms that irritate the gills or skin, leading to flashing or rubbing behavior. Dropsy is a more severe condition where the fish swells and scales may protrude, usually indicating internal organ failure. Viral diseases like Koi Herpesvirus (KHV) are serious and often fatal, spreading quickly in stressed populations. Preventing disease starts with good water quality, proper filtration, and quarantine procedures for new fish. Early detection is key, so regular observation for changes in behavior, appetite, or appearance is crucial.
