I use egg crate its a florescent light defuser it can be found at home depot
it lets your tank breath but keeps fish in
I have a wood frame I built to hold the light mounted to my tank stand I built
some just put 2 hooks in ceiling and hang them with cables
if you look at the tank to the left you can see what I mean that light is hung from ceiling
I'm curious, what size tank is that and what types of corals are you growing?