Sean,
I originally bought an ALL-glass double tube fluorescent light with glass tops with my 75. Before I ever used them, I realized that's not what I wanted for a reef.
Sooooo.... I built a canopy out of 1x8 shelving. I basically made a box, open on the bottom and back. I braced the inside of the corners with 2x4's. If you're thinking of going with MH later, I'd use wider boards or plywood to make a higher canopy. You can find plans for building aquarium canopies on the web by doing a Google search.
Eventually, I mounted 3 shop lights in this hood, giving me 6 40 watt fluorescent bulbs -- a run a couple of actinic bulbs, a couple of daylights, and a couple of 10k's. You can get dual tube shop lights at Home Depot, Lowe's or even Walmart for less than $10. You can also use the Daylight bulbs from HD or Lowe's -- just get the ones that are rated 5,500 to 6,500 Kelvin - for a few dollars each. My whole lighting system, canopy, fixtures and lights cost about $100.
I have over thirty species of corals that are thriving with this lighting.
HTH,
Mariner
