I noticed that my 3 red tail barracudas that I had in a 55 gal. fish tank that I had recently bought had tail/fin rot. I bought Melafix and aquarium salt because everyone seemed to recommend it. i put the recommended dosage in along with the salt and after an hour to my surprise two of my barracudas were dead and one has white film over its eye. My tank has been set up for a month before I bought the fish and it was running at 78 degrees. I also have a 4 inch clown knife, a dragon goby, a pleco, and a marble gar. all seem to be doing fine except the gar lost its color but got it back overnight. Does anyone know if Melafix caused the deaths or if it was something with my tank.