[Scuba_Steve]

The issue your going to have is spotlighting. I am not speaking from any experience with LEDs btw, just what I have read. You will have to space them far enough apart that only a small space under the LED will be lit by the optics. If you choose to go opticless, you will prob overcome this to an extent, but will not have very strong lighting. As a guess, with optics you could keep a colony directly under each light. Without, you can keep low/mod light corals. Pretend you have PCs. Keep the moderate ones up high, and under the LEDs if possible.