Building a canopy for MHs

[Grimmy]

I need to know how far above the MHs need to be from the water surface. I have heard alot of different opinions. So how far should the top of the canopy be from the rim of the tank? Thanx so much.

[MyReef]

I can only give you what I did....my canopy is 13" tall. The lights are about 2" off the canopy top and the reflector is about 6". I just did not want any splash and have a problem with the bulb exploding. I would build the canopy a minimum of 10" total height IMO. HTH good luck.

[HARRISON]

I am no expert but I just asked the same question to my LFS and was told 10 inches above the water. That seems to be the key...Hope that helps. I am putting in new MH as well.

[TroyF]

Lots of fellows run them as little as four inches off the water and one guy has his two inches off the water. I had mine about 6 inches off.

[Emperator]

My canopy is 15" high and my iwasaki's sit about 10" from the water.

[TheFrugalReefer]

Another question about the subject is, what kind of wood to use and treatment (water sealer) to keep the canopy from warping? I just set up my 40 gal. and the top piece, which the PC are mounted on with a reflector, is already warping. I used wood made for a desk. Laminated or veneered. I thought it would keep out the moisture and I even sealed the edges without the veneer with outdoor wood glue. Anyway... I might have to build a new canopy if it worsens. And a reply to the original question... just make sure water doesn't splash onto the bulb or **kaboom**, and you get the shimmer effect when you raise the bulb a bit high.

[reefguy]

usually, despite popular belief, metal halide bulbs won't explode if they are splashed with water. unless you use the two-ended linear bulbs, conventional screw-socket bulbs are actually two bulbs in one. the outer glass envelope protects the electronic components inside, and the bright part is actually the bulb. the outer glass shell is a LOT cooler (even though it doens't seem like it) than the inner bulb. small splashes on the glass envelope reduce the temperature only slightly (probably immeasureably), and i've even heard of bulbs dipping into the water and not exploding! anyway, the thermal shock from small splashing is insignificant and definitely should not make the bulb explode. having said that, my metal halides routinely get small water splashes and i've never had a problem yet. i would be more worried about the waterspots on the glass envelope reducing the light intensity and altering the emitted spectrum. i run my bulbs about 8" off of the water, but the guy at the LFS recommends about 4", if you can achieve that. anyway, hope this helps...