MH Coverage

[spikehs]

I am lookin into setting up and having some troubles on deciding what kind of tank/light combo to go for. I have decided that I want to keep it as simple as possible with minimal lights. So I am tentatively going to go w/ the aquariumlight.com Single 400w mh canopy.

For the tank I am lookin at doing a cube style 30"w x 30"l x 20" h. I know MH are supposed to only be able to cover a 24" square area, but since this is a 400w and it will only be 20" deep i figure I could stretch that a bit by raising it up. I was planning on having a coral island in the middle and nothing on the outter edges so it doesn't need to be full intensity there. My only hesitation is i just dont want it to look too dim on the edges.. Thoughts?

Oh yah, one more quick question. What would be a good turnover for a fuge/sump 5x tank volume? I want it to be quite, so the slower the better...