Prazi is an effective treatment for a variety of parasites, most notably the common protozoan parasite Ichthyophthirius multifiliis. Commonly referred to as white spot disease or ich, it attacks the gills, fins and skin of many freshwater fish species including goldfish, koi and barbs. Prazi works by attacking this parasite at its larvae stage before it can mature into adulthood where it would be much more difficult to treat with conventional medications. It acts as a neurotoxin which disrupts nerve impulses in the developing Ich causing paralysis and death. When used properly, prazi has been shown to be highly effective at eliminating Ich from fish tanks even when other treatments have failed.