Thanks Guys, the yellow tang has only been in the tank for about 1 week. I added him to my 50 gallon to control algae last tuesday, then on this Sat. I moved the whole 50 gallon over to a new 75 gallon, so naturally the tang as well got moved. The reason it raised an eyebrow with me is because I used to have a Yellow tang that had an incredible appetite, eating everything from algae to flakes. Ill give it some more time, I have some SeaChem Garlic Guard I could try but Ill see if he comes around before that.
Think he may be filling up on algae, I have lots of algae on my rocks and he is always grazing.