I'm building a hood for a 110 gallon aquarium that I'm restoring. The lighting I'm going to use will have two 20,000k/250w metal halides as well as two 40w Fluorescent Actinic 03 Blue bulbs. The aquarium is going to be a reef aquarium with hopefully lots of coral. The one thing I'm not sure about is how far away the lights need to be from the water (so I know how tall to make the hood). The shorter the hood the better for design sake, but I want the lights to be as efficient as possible for growing coral. So how far from the water should the lighting be? If anybody could throw some expert advice my way that would be great! Thanks.