When I feed my tank (reefroids) I usually turn off the return pump and the wave box. Then I try and spot feed some of the corals. I noticed that the Millipora gets a slimy coating on it. My question is what is it and should I be feeding it difrently?

Stony corals like Acropora Millipora usually do not require spot feeding.

when they produce excess slime its an indication that they are being irritated.