Microsporadian parasite of the various Pleistophora species causes infections both in fresh and saltwater habitat fish. It effects the commercially important farmed fish eel, sea bream and turbot and also some aquarium fish; commonly neon tetra, angelfish and gold fish. The microsporadian parasite not only affects the fish muscles but also the internal organs and produces small cystic nodules. In this study, a platy fish exhibited loss of coloration in the skin at the left side of the body and translucent area in the muscle that makes visible the visceral organs with naked eye from the outside is observed in the aquarium at cur Fisheries Faculty Ornamental Fish Rearing Unite. Affected muscle tissue turned to white and deformed by the cysts and became very thin. The affected fish liver was found very pale and surrounded with a red coloured haemorrhagic marginal halo around the lobes but the spleen was found to maintain normal coloration. Histologic sections from organs embedded paraffin blocks were prepared and these were stained with Haematoxylin - Eosin. Histopathologically, cystic nodules comprised Pleistophora spp. spores was found in the sick fish tissue of muscle, liver, kidney, spleen and intestine. It was determined that infected tissue cells with the parasite spores was found enlarged hyperthrophic and contained intracellular ovoid shaped spores in the stained tissue sections.