<a href=showthread.php?s=&postid=10236394#post10236394 target=_blank>Originally posted</a> by TheGrog
When I built canopies and stands, I always put the fans on the sides, both blowing in. Here are my reasons for this.
First is that they always will get the least humid air and lengthen their life as the salt mist does not get on and in them and erode the circuitry.
Next, rather than having one in and one out, have both going in. That way you get twice the air flow. For example, if both fans move 50 cf/h, and both are blowing in, you will have 100 cf/h (cubic feet/hour) whereas if one is in and one out you will only have 50 cf/h of air movement.
Last is that the air flow will go across your hot lights which, I assume, are mounted midline in the tank. This provides optimal cooling.
So, I would start by mounting both on the sides blowing in and see how your temps do. If you still want to go lower, add the other two blowing in.....assuming you have some outlet for all that air movement.
Hope this helps.