What are U feeding your SPS's?

[Snappy]

If sps only need to feed on light, why do they ( acro's for example) extend their polyps when the lights are out? I just assumed they were feeding. Why do some of the other sps (mycedium (spelling?) for example) send out sweepers? Is it only to attack other corals? I thought they are trying to feed as well.
I have experimented with feeding and not feeding and it seems my coral's get brighter, look healthier and grow faster when I feed. Is it my imagination? Please tell me if I am wrong. If I am wrong I'll not bother feeding them and start saving some loot.