effect of MH heat under aquarium

[TheMcs]

I've got an open 2x4 rack for my 40Bs, one above the other. The tanks sit on the 2x4s, there is no plywood shelf. I want to place a 250w SE MH under the top tank to light the bottom tank but I don't know if enough heat can accumulate to have any ill affects on the bottom of the top tank. The MH would be mounted to a piece of 1x (with a reflector of course) about 1" below the rim of the top tank. Air circulation will be good and if I proceed with this I'll place a thermometer between the MH mount and the top tank to monitor temps. Any ideas or experiences would be appreciated.

[mabublitz]

you will have quite a bit of heat there, but if you have a fan or two that is ventilating the area most of the heat will dissipate. make sure there is a few inches between the reflector, 1 x1 and the bottom of the top tank.

[maroun.c]

got a 150 W under my tank lighting up my in stand fuge.
1st day I checked for heating on the pleace of wood below the tank and it was a bout to catch fire. a fan directed ont eh halide all the time its running keeps eveerything coold now.
Still wouldn't trust a fan on a 250Whatter as the slightest fan problem causing it to get stuck would quickly result in the bottom pannel of the tank on top breaking due tot he intense heat below it.

[TheMcs]

Thinking I'll mock it up over the weekend and run it while I'm home to monitor temp. Should be no less than 1" between top of 1x & bottom of tank, with reflector the socket the bulb should be about 4" from the glass. I've got a couple 4" fans I can use to move air also.