A method for reducing parasites in aquatic animals is provided. The method includes reducing a plurality of parasites infecting an aquatic animal by administrating to the aquatic animal a compound comprising propyl propane thiosulfonate (PTSO) having the formula R-SOa-S-R, where R represents n-propyl group (-CH2-CH2-CH3) and a is 2. In yet a different embodiment, a method for reducing a plurality of parasites infecting an aquatic animal includes administrating to the aquatic animal a compound comprising and propyl propane thiosulfinate (PTS) having the formula R-SOa-S-R, where R represents n-propyl group (-CH2-CH2-CH3) and a is 1. In even yet another embodiment, a method for preventing a plurality of parasites in aquatic animals is provided and includes administrating to an aquatic animal a compound including PTS. In a different embodiment, a method for preventing a plurality of parasites in aquatic animals is provided and includes administrating to an aquatic animal a compound including PTSO.
