I just treated my 120 gallon reef tank with salifert flatworm exit to get rid of the flatworms that were on all of my corals. After reading the instructions carefully, I removed my carbon,and dosed the appropriate amount recommended. I saw an immediate effect on the worms, lots of movement attempting to get away. I began siphoning the moving worms out and after an hour noticed my 6" purple tang was gasping for air. I immediately returned carbon to the tank and did a large water change, but by then it was too late. I lost my purple tang, a naso and a sailfin tang. All were over 10 years old and were huge. Wish I had seen something earlier that said it was toxic to tange, would have never used it!!!!!