A little blurb I found online... great info

I've never been a big fan of supplemental liquid additives, whether it's for elemental replacement or for nutritional purposes.
Recently however, I got a bottle of DT's to put my own tank through a test to see what I personally felt of the addition. Since I only recently got the bottle, and have added it only once, I don't have much of an input thusfar, but I can give you a bit of an education on feeding corals.

Corals need to feed in order to fulfill thier daily energy needs. Most of these needs are met by the huge amounts of light we place over our aquariums, but usually not all of them. Without having a full day's supply of energy needed, the coral will slowly withdraw over time, as it is shrinking instead of growing. It will continue to do this until it meets it's daily needs or it perishes from the effort. So how can the coral get this extra energy it needs? By feeding, that's how.
We can even go a bit further by adding that any energy gathered above and beyond that required for it's daily functions is then utilized as further growth for that coral.

So the question remains....What should I feed my corals??!!?
Well, the types of food all depend on the types of corals in question. Most of your Large Polyp Sleractinians, or LPS corals, can be fed chunks of seafood. Corals falling into this group would be those similar to the bubble corals, open brain corals, Caulatrea, and other fleshy corals with large visible mouths.
Other corals, such as muchrooms, leathers, xenia, and polyps actually like a little more dissolved organics (read nutrients) in the water, as they feed on this matter, as well as phytoplankton, as it passes by. I personally feel that extremely heavy skimming is rather harmful to these organisms by removing much of the food matter that they thrive upon. I advocate skimming, but not overskimming, to clarify.
Many of your non-photosynthetic gorgonians would also fall into this group. A good rule of thumb is that if it has white polyps, it will need to be fed foods such as phytoplankton, as they are unable to utilize the light as a source of energy. Therefore, all energy comes from captured foodstuffs.
SPS corals, or small polyped scleractinian, utilize lots of light, as well as more of a meat-based diet, which consists of zooplankton. Zooplankton are simply the smallest forms of animal in the water column that feed upon the phytoplankton. Sps corals will also feed on particulate matter in the water column, such as that blown out of the rocks on a frequent basis to help fight nutrient buildups. This is probably the single-most efficient feeding that you can give your corals, all the while removing excess waste from your tank.
As you can see, corals are vastly different and thus need to be accomodated as such if they have any chance of survival.