Dont go with advice from LFS
Firstly on corals there are many many different types and species to consider and the different types require different care. For instant soft corals and mushrooms can be kept under T5 lamps very well however SPS
and Inverts need a stronger light such as Metal Halide or LED
There's plenty of sites that have information on corals. The annoying part is spending time researching. I stick my head in a book on marine life (or many books) and that tends to help also.
Finally corals get their 'food' from light. Just like plants they use photosynthesis. There is no need to supplement with coral foods if your lighting is good enough.