Why would that have an affect on the life span of the bulb? :confused:

Bulbs need to run at certain temps to put out the correct spectrum. Not sure about affecting life span, but if you've ever touched a MH bulb, you'll be with me in thinking some puny little fan isn't going to do squat for cooling it!! These bulbs run somewhere around 700 degrees, a fan isn't going to cool it off any appreciable amount.

your actually better off turning the fan around so you can pull the hot air out instead blowing it into the the hood.

Depends on your purpose for fans. Mine was to encourage evaporative cooling, and the greater the velocity of air across the surface of the water, the more water evaporates.
I also think that removing air hot air from the canopy is pointless, as soon as the new cooler air enters, the bulbs heat it instantly.
Overall though, as with the rest of the hobby, whatever works for the individual is the right way. :razz:

I do it because it drops the temp of the inside of my stand by 15 degrees, some of us have doors on ours :mrgreen:

Steve

Doors? I don't need no stinkin' doors!! Quality cardboard flap that's lasted 2 years now.

Hey the new tank has doors right? :wink:

Steve

Ya, but I'm gonna take them off and build new cardboard flaps. Just for you!!

LOL, are you sure you arn't doing that just to have more light to read by?

Steve