Canopy Questions

[Stoll]

Hello everyone. Lately I've been considering building a canopy for my 75gallon system, mainly because my 4-65w PC Coralife fixture is looking pretty sad. I do plan on upgrading to MH lighting sometime in the near future, and I intend on gutting my current fixture and using the PC's in the canopy as well.

I work in an Architectural office, so modeling my ideas is fast and easy. I had originally thought of having the light mounting panel hinged at the back so I could tilt it up at need, and then doors on the front that hinge at the top. I was thinking of 2 fans, one in each end of the canopy. My current design allows for 6" above the bottom frame (2x4 atm) for fan mounting, and another 6" to the u/s of the light mounting panel. This would put the lights at around 16-18" above the water, which to me seems a bit much. I had the idea of mounting the PC and MH ballasts on the top of the light mounting panel but I wouldn't want them visible from the front. I'd then need a bunch more height to conceal them, making the entire canopy a little over 2' tall. Add that 2' to the overall height and I'll need a chair to get at the top of the canopy for maintenance. I'm now wondering if I should just build a small stand to store the ballasts in to reduce the height of the canopy, not to mention trying to contain some of the noise a little better.

After all that, I suppose at the moment my questions are these:

1.) How high above the water do you generally mount MH's (thinking of using 2 x 175's). I live in the Okanagan, so it's hot here in the summer and I currently lack air conditioning, so heat is a definite factor. If I need to install 4 fans (possible?) I will as a chiller is an expensive commodity.

2.) I've read that most MH Bulbs are designed to run at a certain temperature so it's not a good idea to have the flows blowing directly across them, meaning I would need to allow some extra height in the canopy for this. Is this generally true and what kind of clearance should I allow? Anything I can do to save height would be great.

Any and all opinions or ideas are welcome as I'm sure I haven't managed to think of everything!

Thanks a bunch!