i feed my tangs the two squares mainly cause of their size my yellow is fairly large and he doesnt graze like he use to theres not much left to graze as of recently and plus their not the only algae eaters in there just about all my fish are grazers if not always than at times
not sure on your set up but mine has a fair bit of flow and a good turnover to my sump so i imagine most of my fish waste is gone right away between that and my livestock