Fusarium spp. are types of fungi that invade agriculturally important grains, such as corn and wheat, where they may produce mycotoxins that are harmful to the productivity and health of food animals, such as swine, poultry, and aquacultural fish. Because corn and wheat are used for other industrial purposes, such as ethanol and flour production, by-products of these processes are available to supplement or replace expensive grains in fish feed formulations. Consequently, grain by-products have come under scrutiny as possible sources of feed-borne Fusarium mycotoxins. Evaluation of the effects of Fusarium mycotoxins on productivity of fish used in aquaculture has been the subject of recent research.