I'll pitch in; I don't have a lot of SPS experience but passing on info that I read (and am currently using as a guideline) my single 250w DE bulb is currently 12-14" off the surface, with the bottom of the fixture about 6-8" up. Like others my fixture is suspended by chain that allows for about 6" adjustment to accomodate varying light levels as the bulb ages. I try to keep a minimum of 12" between the bulb and the water surface to minimized the amount of heat that ends up in the tank. With the pheonix 14k bulb in my DIY fixture I get about 40000Lux at the surface, about 13500Lux just into the water, about 8,000 mid-tank and about 4,000 at the bottom. My tank is 24" tall.
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