Here's how I kept my 12 gallon durabox bins cool (about 8 or 9 degrees cooler than the cabinet temperature, filled to 8 actual gallons of water with 1-8" round airstone blowing out .5 cfm of bubbles) in a very small (2'W x 3'H x 18"D) space with a 250 watt hortilux blue bulb running 24/7. I drilled 4" holes (about ten of them) that coincided to half lap the edges of the perimeter where the tank stood (so the air would blow in from the floor and out a 4" can fan HO no carbon and it wasn't even ducted outside because the exhaust was passively sucked into the flowering room) and I put a double layer of 3/4" Mylar coated white polystyrene foam over this bubble cloner/veg chamber (the Polyshield foam was like one big bin lid and holding collar for all the clones , you would just lift them out via means of a pre-perforated 1-1/2" circle that surrounded each clone) and the foam lid would extend about 7" to the left and right of the bin. I cut some holes through the Polyshield foam past the edges of the left and right side of the bin to allow the air to pass (but I didn't cut the holes big enough to eliminate negative pressure , you gotta make that exhaust fan yearn for a little more air). Here's why it worked and why it proved beyond the shadow of a doubt that the "raised floor" method of venting works. The hot air being produced by the bulb could not transfer enough heat through the low density (tightly closed but with a few little air spaces from the holes that held the clone stems) foam lid because the fresh air that blew through the .5 cfm output of the stone created an air pressure (a very low pressure but high enough) that forced its way through the many little holes in the foam lid and the combination of conductive heat transfer between the foam lid and the air passing through from the air stone wouldn't allow much of the incoming air (not the air from the stone , rather the air from the intake holes on either side near the edges of the bin)which has no choice to mix with the heat of the bulb because the space was so tight. So the incoming air and heat from the bulb would for the most part take the path of least resistance out the exhaust fan and the little bit of air rushing through the foam lid holes would not allow the ambient air of the cabinet to enter the airspace between the foam lid and the water surface. Mind you that I took care to place the air stone pump in another room which had no heat source. The bin was literally 18" away from the bulb but it didn't heat up the bin. Bottom to top ventilation. It will cool the room and your reservoir.
