it depends on my corals. a lot of them i dont feed at all. some others that i want to grow fast, such as my duncan, i feed about every other day.
as far as time of day, it also depends on the coral and what time of day they are open more. some of mine are most open when the halides are on, others, not so much.
what types of corals are you lookign to feed and what are you thinking of feeding them?