That is what I do. No one or no fish would like to eat only lettuce everyday. And once a week soak your food in Selcon or some other Vitamin liquid,So get maybe 3 diffrent foods? One flake one pellet andmaybe one frozen and do one monday, other on wesday and last one on fridays?
IMO two tangs would do good in a 75 and thats the yellow tang and a yellow eyed kole tang.
My LFS has a blue tang in a 75g, along with the biggest Clown I've ever seen. If it's smaller than 3", I'd be surpriced. The tang is about 5". It's been in there since my first visit in March.