Just finished treating a hippo tang with this med. He was in very bad shape but still eating. The tank he was a 30 gal. and had lr ,some sps frags, a clam,hermits and snails.The med. didn`t bother anyone. I heard that it works better in small tanks. Just a note the fish were bought about a month ago so another instance where qt definatly helped. The sight is www.nosickfish.com Tim......