Like all tangs they need a large proportion of algae in their diet, but also should have meat. I would suggest 1) New Life Spectrums Salt water pellets (best food out there) 2)Frozen mysis shrimp and...
Tang Fish are technically classed as 'herbivore', and in the wild their diet consists largely of algae, such as caulerpa and gracilias. In aquariums they still need their diet to be mainly algae....