How high off water for 1000w?

[Ctsaltwaterguy]

I am running 6 - 48"x24"x12"Deep frag tubs with eggcrate shelf 2" off bottom. The light is a 20" square reflector with 20k 1000w bulb that is on a hydroponics light rail. It is adjustable in height and time it takes to move the 9'. Any ideas as to what height I should start out at for LPS/Clams?

 

[JNye]

sounds like a serious set-up. Why guess, get a quantum meter. But if I had to guess I'd say start at least 12" above the surface.