I feed my five Chromis and Powder Blue Tang a half cube of Marine Cuizine a day after work, as well as a few pinches of flakes in the morning and they are healthy and growing. I think a half cube would be more than enough for your purposes as well. I feed dried algea via veggie clip to the Tang each day as well, but you don't need that.
65gal drilled Reef (3'x1.5'x2').
1 Powder Blue Tang, 1 Yellow Eyed Kole Tang, 2 Ocellaris Clownfish, 1 Talbot Damsel, 1 YWG, 1 Red Honey Damsel.