Agree with melosu58... if you're just keeping soft corals (mushrooms, zoas, leathers) and LPS corals, you can probably get by with just normal PWCs. Some LPS corals don't mind being fed small bits of food like mysis or cyclopeeze - the same stuff you'd feed your fish. But this can be done with just spot feeding.
If you're keeping SPS corals, that might be a different story. Depending on how many you have, you may have to supplement various elements. I don't do SPS, so I don't have specifics for you.
Personally, I keep zoas, mushrooms, and various LPS. The only thing I "supplement" is a 2-part Ca/Alk solution to keep my Ca levels even through the week. I have a fair amount of coralline algae on my rocks and like it! It's a big calcium hog! I do spot feed some of my LPS though, but I don't add any "coral food" or anything else to the water.