light question

[shrimpin]

I have a 150w MH over a 18 inch deep tank and the fixture hangs 7 inches from the water, my question is how low in the take can I keep SPS?? Right now I have them in mid-high level of the tank, just curious if I can go lower....

 

[WinnipegDragon]

With only 18" of depth, you should be good pretty much all the way to the sandbed, even with a 150w.