I have a couple of questions about a DIY canopy I want to make. I'd like to make it a combination PC/MH canopy. It is a 4' X 18" top and I plan on putting 4 X 55W PC's in two rows front and back. Then I'd like the option to add metal halides at a later date in the center between the two PC rows. I've seen hoods like this on reef tanks and like the flexibility this creates. Problem #1: The metal halides require more space above the water. I've heard 6" is sufficient, but that would put my PC's a good 30" above the bottom of the tank! I am thinking I will have to drop a tier for the PC's, but I was wondering if anyone else had this type of setup. Problem #2: I don't think this setup would work on type of a glass canopy for obvious reasons (heat, space, etc.) and I am expecting to have to put in fans for the MH's. In any case, are there any problems with the PC kits from AH Supply as far as condensation from a canopy without a glass top, and how much ventilation is necessary with just the PC's? I'm sure the answer will be "you'll have to play it by ear" because of all of the variables (ie. heat, space, equipment, condensation, ease of access, etc.) but any pointers would be appreciated.