overheating question

[Sea monkey]

I want to set up a couple of tanks in my basement to do an experiment and planed on using a 2x250 MH i have laying around . I'd like to use small tanks for this. how small is too small before i would have issues with the lights overheating the water. BTW the basement stays rather cool all year round.

[gwen_o_lyn]

I have a 150w mh fixture with a fan over a 12 gal nano.
The tank increases in heat about 4-5 degrees and the light is currently on a 9 hour cycle.
So I'd say bigger than 12gal and prolly bigger than 20 gal.

[Sea monkey]

to make it more difficult id prefer not to put a fan on the tanks either . i got too much evaporation as it is : (

[happy]

put a good size fan on the lights, that way the only heat transfer is from the light, which many animals will be able to handle, since in nature, a shallow area will heat up with the sun anyway. you can also run a fan on the glass part of the tanks, it will cool without evaparation as long as it doesn't hit the water surface.