There's alot of information about coral feeding so you may want to do a web search. Especially wetwebmedia.
Your question is too broad for any one answer. Some corals need feeding if your tank isn't supplying enough food. Some get almost all of their nutrition from light. Some can only eat very small particles while others can eat large particles.
Just too many variabilities. Best to see what the needs of 'your' corals are and go from there.
Good Luck!