Public hatcheries in the United States, including facilities culturing threatened and endangered fish, are severely restricted by the lack of legally approved medicinal drugs to treat diseased fish and fish eggs. Formalin was identified by state and federal hatcheries as an urgently needed drug that would be used to reduce disease-related mortalities and improve production efficiency and product quality at public hatcheries.

Studies required by the Food and Drug Administration were conducted to allow the approved use of formalin on all finfish and all finfish eggs cultured in public hatcheries.  Formalin is used as an external parasiticide to control protozoan parasites and monogentic trematodes on finfish.  For finfish eggs, formalin is used to control mortality associated with fungal infestations.