Trunkster,
People are trying to tell you what you need to do to keep your tank "healthy" not just survive. You absolutely need to listen to the people on this board and for the majority of the time they are 100% correct. The minimum tank size is 70 gallons, and most will say 100 gallons is the minimum. Their adult size is up to 1 foot. So your tank is absolutely too small for a tang period. Just cause it looks fine now doesn' mean it is. How long have you had it? You can measure success is this hobby by years not weeks or days. I don't mean to be too harsh, but do the fish a favor and return him to the LFS and get one when you get the bigger tank. Sure your tang may live for a few months like that but it won't be a happy fish.