How high should my light be over a 12" tank?

[Brian94558]

I have a 17g tank that is 12" high with a 150w MH hung over it. I was wondering what would be the ideal height for it? I have sps towards the top of my tank and lps on the sand bed. Right now I have it at 16"s above the water line.

[mike_cmu04]

If everything is doing good i would leave it where it is. If you do lower it i would not go lower than 12"