Listen to Sepulatian. Before I frequented these boards, I bought a purple tang for my 58. He did fine for about 7 months, but has since developed HLLE. I have since moved him to QT, am feeding a variety diet and making frequent water changes. Fins have returned to normal, but he still has HLLE, although I think it is getting better. My ultimate goal is to trade him or return him to my LFS (although they did sell him to me and say he would be fine in my tank, so it will be conditional on them selling to someone with at least a 90gal).