Freshwater dip or bath treatment has been found to be very useful for treatment of several types of ectoparasites that occur on marine fish. Under certain circumstances when tilapia are raised in brackish or saltwater, infection of these fish can occur by obligate marine ectoparasites. In Hawaii, tilapia raised in saltwater have been found infected with Caligus sp.; Neobenedenia sp., a large monogenetic trematode that infest the skin and Amyloodinium sp., a single celled ectoparasite found on the gills and cuticular surfaces.
Tilapia can live in both fresh and salt water. Depending on the parasite involved and other circumstances, freshwater treatment may be given either as a short duration dip or as a prolonged, two weeks or longer, bath.For example, tilapia raised in saltwater cages placed in natural bodies of water may need to be periodically dipped in freshwater to remove Neobenedenia sp. However, tilapia captured from near-shore marine waters for use in laboratory studies can first be "cleaned" of marine parasites like Caligus sp. or Amyloodinium sp. by slowly transferring and holding the fish freshwater for a period of several weeks.