Dual 400w with 10k over 75 gal

[newbie]

Can anyone tell me what problems I might have running 2 X 400w 10K MH's over a 75 gallon tank. What height should they be off the water? I just picked up 2 ballasts and will be making enclosures for them as well as a new canopy. I am looking to put the lights 8 to 10 inches above the water with 2 doors on the front of the canopy for access.

[Reefland]

Heat will be the main problem, and of course coral acclimation for new acquires. I would place the lights 11-15" from the surface and make sure that you have plenty of fans to vent the enclosure. If this doesn't keep the tank cool enough you will have to look into a chiller.

[Poseidon]

I can almost GUARENTEE the need for a chiller! I have 2 250W 10K's over my 90 with a 30 gallon sump, and I had temp very near 90! With the canopy open I could manage 84-85 as long as it is not hot in the house too!

I think Scott is right about the height too, my bulbs sit about 7" off the water. I am quite sure that contributes to the heat problem.

[newbie]

Well house temp is not a problem, central A/C @ 74 degrees. As for the hood, i was kinda hoping to mount the lights in the top of the unit and leaving the top panel that would cover the lights open. its a shame I can not get away with just 1.

[charlie]

You will probably have heat problems unless they are at least 13" of the water surface. Are you going to install any fans in the canopy?