Hi:
I have a little pocket book I carry around like a bible. It tells you what to feed the fish and who gets along with who and tank compability. I'd be lost without it. It's Marine Fishes by Scott W. Michael.
My handy dandy little book says to feed power blue tang a varied diet mostly vegetable matter. Dried of frozen herbivore foods that containe marine algae and blud green alga. You can supplement with zucchini, broccoli, and lettuce. Feed three times a day.
Well that's what the book says......
I have a naso tang who eats similar foods. I feed him flake in the
morning and frozen at night and a small amount of marine algae daily. Tangs need the algae for color, but some other foods for a balanced diet.
Good luck with your tang. They are beautiful and entertaining fish.