True, most corals, stony or not share a symbiotic relationship with zooxanthellae (SP?)(zoo-zan-thee-lay) which is an algae that the coral feeds upon. That algae needs light to grow, so feedings are not necessarily dire. BUT, I imagine that if you feed them it probably helps them to grow faster.

I could use a hoborichardpingtexreefbirdstreepguy answer here to help give a better idea. I too could use some schooling here.