Ya, I had originally though MHs needed to be 8" off the tank then I asked my LFS that I trust and he stated 250's need to be a min of 12" or else you will fry the corals. Something about to much UV light from the MHs burning the corals if they are too close. This is just what I was told though.. so take it for what its worth. I would definately like to hear other opinions as well.
You seen my blog salty, that one pic of the zoas was taken under 420's. They normally do not look like that under day light, but once the dusk/dawn setting kicks in to just actinic mode, they really shine.
Never heard that before...I always ran my 250w at 8 inches, never had any problems with the corals in there....The UV is not a problem because the glass that "should" be used with a MH lamp is also a UV filter...