how long did you have the fish> I had a wonderfull purple tang, very healthy, ate anything, fat and happy. After two months i woke up to find him dead in the rocks. I think this was caused by the way the catch the fish. Prob used something to make him sleep. Sometimes they die right away, some times it takes a long time. I had another tang, a naso that i got from mr coral. He was a puppy dog. Followed me around when i was looking for frags and squirted water at me, sigh, had to buy him. Turned out to be an excellent fish. One day he just quit eating after i had him for a month or two. He was very fat and was waisting away. This all from a fish that ate like a pig. After two weeks of worrying he finally started to eat again and has been doing fine since. We can only controll what goes on in our tanks, but the people who catch these fish are know to use toxins that not only harm the fish but harm the reef also.