Potassium permanganate (KMnO4) or PP as it is sometimes called is used as an external parasiticide, fungicide, and bactericide. It is a strong oxidizing agent and “burns” organic material off the external surface of the fish. Some of the external parasites PP works on are Trichodina, Costia and Chilodonella. In addition to being an effective anti-parasite treatment, Potassium Permanganate can also assist with bacterial gill disease and other bacteria like Aeromonas and Pseudomonas bacteria that can cause skin ulcers. It will also oxidize dissolved organic matter, reducing the biological oxygen demand and improving water quality and clarity.