Some tangs will eat it, my Yellow doesn't seem to though. My lawnmower keeps a couple rocks around his favorite perch spotless. Best way to get rid of any algae, and keep it away, is to starve it. Cut back on your feeding and increase your water changes. I know, I don't like that answer either, I've got a tank that despite cutting my feed portions in half, and cutting their frequency in half, still has hair algae problems.
Also, how big is your tank? Most Tangs get pretty big.
Phil