How high to hang Giesemann Spectra?

[Zstriker]

Any spectra or perhaps infiniti users out there? Looking for advice on how high to hang the fixture above the tank. It is SPS dominant, shallow (18 inches), and the fixture currently has 2 250w radiums, 2 blue pluses, 1 purple plus, and 1 aquablue special.

Thanks

[moondoggy4]

When I was running MH's I kept my bulbs 9'' off the water. The Spectra's are adjustable with there hanging kit.