[cubalz]

Hello all, I have a 90 gal tank with a Custom Sealife 260 watt compact florescent fixture with built in ballasts and 2 100 watt VHO's inside my canopy. They provide great lighting but I have sooo much heat built up in the canopy that raises my water temp 2-3 degrees. On e-bay I just bought a twin 3" fan setup that has a heat sensor that makes them go faster as the heat builds up.
OK here is my question- What is better, having the fans set up to blow in cool air over the ballast and lights that are in the canopy or having the fans turned around and suck out the hot air out of the canopy?

I am not sure which will be best. Any help anyone could give me would be appreciated!

John

[Poseidon]

How about a THIRD option, 1 to pull air out, the other to push air IN... That way you get a constant "breeze". I think that will give you the most effective cooling.

[cubalz]

Cool! I did not think of that. I will give that a try and let you know how it works.

Originally Posted by Poseidon

How about a THIRD option, 1 to pull air out, the other to push air IN... That way you get a constant "breeze". I think that will give you the most effective cooling.

[Drew]

Actually you are better off with both fans blowing in. Having one blow in and one blow out is kind of redundant. For example, say you have 2 fans that move 100 cfm each. With one blowing in and one blowing out you are still only moving 100cfm through the hood. With both fans blowing in and somewhere for the air to exhaust you are moving 200 cfm through the hood.

Later
Drew

[daltex]

i agree with Poesidon and I think circulation is the key. The only catch is sealing the air movement in the hood. Not totally sealing it just the major gaps. If not the circulation theory will fail and you “output” fan will bee worthless.

[Drew]

Agreed, circulation is the key, but you will get more circulation with both fans on one end blowing in. As you stated it needs to be sealed except for at the other end where the full volume of air can escape. Simple physics, you do not need a fan to pull the air out. It has to go out somehwere if you are increasing the pressure inside the hood with both blowing in. Make the only exit at the opposite end you will have perfect circulation with twice the airflow.

[Reefland]

I've ran both in the past. I if the hood has plenty of places for air to escape, both blowing in is a good idea. If the hood is totally enclosed with no openings, I would turn one in and the other out.

Scott Z.