Lighting Spacing

[dmilligan]

I currently have a 29 gallon reef with a hamilton 24" VHO system. I was thinking of supplementing this with 175 or 250 watts of MH. Is there any minimum spacing between bulbs? What I would probably end up with is the MH in the middle and the a VHO tube running down the front and back. With the 29 gallon, the front to back spacing is around 11". I have read the MH's run hot so I wasnt sure if that might affect the VHO's. Any insight is appreciated.

Thanks,