i just got done dosing my 75g with melafix. just like all medicines becareful to get the dosage right(compensate for approx. rock volume and sump) turn off carbon and skimmer and follow the directions. i dont have anything special in that tank so my risk was not too great, even though it was a little touch and go, my gorgonias survived. i did a 5 day treatment and all went well. fish looks good. make sure you have fresh carbon on hand once the treatment is finished. good luck