Since I am in my planning stage for my 2' X 2' x 1' (LXWXH) aquarium, I was planning on doing Halide lighting as I plan on keeping SPS and Clams. I have seen some shallow tanks similar to what I want to do, and the Halide pendant (mogul style bulbs) fixtures were placed maybe 8-12 inches above the tank. The HQI's were placed higher, maybe 18" above the tank. I want to have adequate light for my inhabitants, but have the bulbs low enough that my entire condo is not bathed in light (I know that is hard to do with Halides). Do HQI's produce more output of heat and light then a standard Halide (Lets say for example a 175W Halide vs. a 150W HQI) and is this why they need to be placed farther from the top of the tank?