would you care to elaborate please. i have owned 10-12 scombs and now 3 red tails and i have used antibiotics on all of them as well as prazi pro and quick cure from time to time. And the only negative thing that happened was that i killed my Bio-bacteria before i learned to use the antibiotics in the hospital tank only. I bought 2 red tails a few months ago that were in really bad shape and kept them in a hospital tank with daily maracyn and maracyn2 treatments for 2 weeks and then prazi pro treatments for another 2 weeks. And salt the whole time. And they recovered great. I have had such great success with maracyn and 2 that i now add it in the bag at the lfs when purchasing a new fish so that it is being treated right away and all thru the drip acclimation. I had allways heard not to use antibiotics and i lost several fish to bacterial related illnesses before i tried it.