There really isn't anything that states exactly, that I am aware of. Most things you get coral wise will either have low, medium or high light requirments. Watts per gallon is really not a exact measurment but IMO to give a little comparison I would say 1-3 watts per gallon would be low light, 4-6 medium 7-10 high. If you look on this site at corals and anemones it will tell you what the lighting requirment is. Live rock really does not have a lighting requrment. VHO, PC and Metal Halide are the types of lighting systems most people use. Metal halide is IMO the best you can get it pentrates the water and comes as close as you can get to simulating actual sunlight. If you want high light demanding things it is the way to go. I used PC for a long time and I really liked it. I now have a Metal halide PC combo and it makes things grow and look even better.