I make a mix of foods:
Microvert (Kent)
Phyto (live)
Cyclopeeze (frozen)
Baby brine shrimp (frozen)
Cyclops (frozen - I know it's fresh water food, but they take it in)
Mysis (frozen - more for fish than corals)
What type of coral are you talking about?
SPS will require the likes of:
oyster eggs
DT's phytoplankton
cyclopeeze (I prefer frozen)
frozen rotifers
LPS can live on:
all the above
frozen mysis
frozen daphnia
frozen bloodworms
frozen enriched brine shrimp
Softies can be sustained on all the above (mostly the same as the SPS diet though). Believe it or not, I've seen zoo polyps suck down a piece of mysis shrimp. So anything smaller than that would work.