canopy fans


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Ok so for the people who have canopy fans, how sdo you have yours setup? I upgraded to a Halide on my anemone tank and its getting kinda hot. Do you have them on the sides or top? I'm thinkin of putting one on eash side, the canopy is on a 25Tall so its only 24" long. My real question would be, do you have one blowing air in and the other side sucking air out, or both blowing air in? Also the back of the canopy is completely open. Thanks.

Lee - glxtrix
From everthing I've read, people suggest using the fans to blow fresh air into the canopy. When you blow air out, you're also moving microscopic saltwater droplets. The salt gets into the fan motors and corrodes them leading to premature failure.

Not sure about the top or sides issue. Maybe it would make sense to suck cool air in on the sides and exhaust in on top. Since hot air rises and cool air sinks, you'd be less likely to suck in the already warm exhaust air.
well on my previous 120 i was running dual 250w metal halides, my canopy was closed on all sides so i had two fans installed on the back of the canopy both were blowing air in, i did not have a single issue with heat. I had tried the idea of having one blowing in air and another blowing out but that resulted in more heat and i found my self cleaning a lot of salt creep off of the fan that blew air out, also the fan that blew air out did not last too long.
kinda along the lines of what CGill said, makes sense. Guess I could try to put them on the back of the canopy where it is open blowing in. Thanks guys :)
Seems to me it would depend a lot on the type of hood you have. My hood has an open back with enclosed top, sides, and front. Other hoods are almost completely enclosed while still others have open tops. Heat is going to want to rise so I would think that it would be best to at least have a fan or two or at least an exhaust in the top if your hood has a top to it. Fans work really well to pull down the temperature of the water when directed to blow across the waters surface. This will cause evaporation and help cool your tank water. Just be sure to watch the salinity and level of water in your sump. :)
I am putting together a 120 gal reef tank and also building the hood. I will be running 2 - 400w MH and 4 - 65w Pc's. I am going to set my hood up with 3 fans on each side blowing air in. Hopefully I will not have and heating issues.
As a former firefighter I can attest to the effectiveness of "positive pressure ventilation". This is what I am doing on my 135 with an open backed hood. I have a fan on each end, both blowing INTO and ACROSS the surface of the water. As stated above, a fan blowing out is redundant as well as a waste. If air is being injected into the space, then air (and heat) will get out! If it is not getting out then the positive pressure fans are spinning for nothing. Why wasste the energy of one fan by blowing it out when the hot air will get out anyway? Use the energy of that fan as another source of cool air INTO the hood.
yeah thats what I have going on now, just a basic computer fan hooked up to a dc to ac converter and plugged into a timer. Have it drilled into the side of the canopy. Seeing its only for a 25g, the use of only 1 fan for me is great. Temp never gets over 80.5
One more option to consider. I have my MH lights and the fans all plugged into one power strip. That strip is on a single timer at the wall. This way the lights and fans come on and go off at the same time and only one timer is needed!