Originally Posted by rhino
When i built my canopy i placed them on each side of the frame. I went from a temp sing of 5 degrees to no swing. I used 2 4" computer fans. One piece of advice is that they came with a cover and a piece of thin foam to act as a filter. I removed both of these and the flow increased dramatically and the sound they put off decreased.
Well if you left that thin foam in place it would help and prevent from pulling any dust etc into the tank..... Its surprising at just how much junk that thin foam filter catches. There is really more to those muffin fans than just them being a fan. There are ball bearing type, there is bushing type. There is high speed high vol as well as lower speed hi vol and lower speed low vol. They operate at all rates of rpms, and can be found with 4, 5, 6, 7, 8 or even more blades. Look for fan rpm range, and the decibels they produce....Its a lot nicer to have a fan that operates at say 3,000 rpm and moved 32 cf of air and is nice and quiet that costs $5.00 than one that moves 90 cf of air at 8,900 rpm and is so noisy it has to be operated at a much lower voltage rate just to hear your self think, and it only cost $4.50. Personally I would use a filter and grille / guard. Heck they even make LED illuminated fans in a wide choice of decoratore flourescent colors. I shoot for a fan that operates at full DC voltage and produces low decibels. I can always slow it down to provide less cooling capcity withut incresaing operating noises. Its much easier to slow a fan down to cool less if needed than have to operate it at low speeds and not have sufficient cooling just to get peace and quiet. I also olike to use a variable voltage power source. This enables you to slow down the fan by sliding the switch to a lower voltage if needed, and this often helps to fine tune cooling requirments. Most will operate form 4.7 volts to 12 or so volts without any problems. The cheapest I have seen any of these fans for is at the (surpluscenter dot.) place. As little as a buck or two, for a fan. Then again selection is not always what yu may be looking for exactly but they ought to be pretty darn close one way or another.