What do you have in your tank for inverts, etc? Before you start adding stuff. These fish get ick all the time. My 3 tangs get it constantly and I do nothing, but I have a UV sterilizer which is very helpful in battling ich. Has long as the fish doesnt stop eating he will get over it. If you dont have corals you can treat them in the QT. Also a freshwater dip wouldnt hurt either.