I feed three times per day plus algae sheets for my grazers to have as they want 2-3 times per week and, nem food 2 times per week. Really depends on what you have in the tank. Tangs are grazers so, if once a day, provide algae sheets or nori for them to graze on. Wrasse are fine once per day but, prefer two or three smaller meals. Clowns like to nibble off and on all day, browsers more than grazers so, again more small feedings suits them better.
The algae may be due to lights being on too long white 8 hrs and moonlight (blue) up to 12 hours per day would help that, as would carbon dosing (I prefer vodka) but, if you don't dose now, build the amount you dose slowly, a couple of drops more every 3 days to get to what the tank needs.