First step is stop dumping stuff into your tank. If you don't know if it's needed, or don't know what it's for... then stop. Good water and good lighting is all coral really need to thrive. If there's fish in the tank, they'll find enough to eat. And once you get coral and understand WHAT they eat (they all don't eat the same stuff), then you can spot feed them if you want. But just dumping in stuff that is advertised to "help" usually just fouls up your water and causes more problems down the road.;
OK - now that you've stopped, now the research begins.
What type of corals do you want to keep? If you want the ability to keep anything and everything, then most likely you'll want metal halide lighting for a tank that size. High Output T5 (T5HO) fluorescent lighting will give you quite a range also. If you're only interested in LPS
corals and not high-light demanding SPS
, then you can get by with compact fluorescent lighting.