Ich, also known as white spot disease, is a parasitic infection caused by the external protozoan parasite Ichthyophthirius multifiliis. The parasite attaches to the fishs fins, body, and gills by forming a tiny white capsule, usually less than 1 mm in diameter. The white spots on the fishs body, fins, and gills are the most common symptom of Ich, and they often resemble white grains of salt or sugar scattered over the fishs body. Other symptoms of Ich on fish include rubbing or scratching against decorations or other items in the aquarium, hiding, and refusing to eat. It is important to note that there are other non-parasitic causes of white spots on fish that need to be ruled out before treatment is initiated. Understanding the parasites life cycle is critical to successful treatment. Ich is a common parasitic infection of freshwater fish and is one of the few fish parasites that can be seen with the naked eye. It is treatable, but it is difficult to heal a fish infected with Ich.