Welcome Adventureseeker! Others are sure to have links - and Reeflady has her own recipie... Your question is open to both fish and coral interpretation.
For corals (an fish I presume) you will hear folks suggest you switch out various different foods so as to keep a well rounded and balanced nutritional diet. We use a home-made mush of fish and shellfish from a recipie in Eric Borneman's great book "Aquarium Corals; Selection, Husbandry and Natural History." His book articulates the feeding needs for each coral he catalogs. Everything seems to love the mush.
We switch that out with a commercial formula - frozen cubes - we get at our LFS. Twice a week I put phytoplancton into the water column. And I switch that out with something called Coral Heaven from Indo Pacific Sea Farm (the jury is out for me on this item -- it was a free sample in another shipment)
For the fish -- well they seem pretty happy with the chunks in the coral mush. To that we add some pellets that promote good color. We also use flakes on occation, again, just to keep things interesting and varied. Scott Michael's book "Reef Fishes" is a great reference that will cite specific care needs for countless fish species. It will also help you with species compatability questions.
The thing to keep in mind is LESS IS MORE when it comes to feeding. So you really need to be observant as to what quantity of food can be eaten by your tank inhabitants in a brief period of time. Go slow. They are tiny creatures that do not follow the US penchant for 'super-sizing' everything. That will just foul your water quality.
While our fish are always 'begging' for food, I think it is safe to say they are getting fed plenty and that fish that are always acting hungry are healthy fish.
Oh, and I should add that we also use seaweed for our Tang (s/he's a vegetarian - but not that stricct a one
s/he seemes to eat most anything. But s/he loves the piece of seaweed we put in there periodically.
Anyway - that should get things started.
