You need to make sure that he gets lots and lots of plant matter. This can come from Macroalgae, Sea Veggies, Nori or a high quality food like New Life Spectrum. I feed mine a small piece of Sea Veggies or Nori rubber-banded to a rock and I drop it in. This way he can snack on it all day long (as tangs do in the wild.) You tang will loose his color and develop head an lateral line disease if he gets malnourished. That's why I supplement the veggies with New Life Spectrum. Just to make sure he's got all his vitamins and minerals.