I think it should be no problem. Put the air pump to the nipple on the side under the skimmer cup. The air first has to pass under the cup and then down through the regulator and silencer and then the venturi. I think the feedback/silencing system gives plenty of time for the air to warm up. I would be more fearful of the airpump suffering from the cold. If you can buy a Coralife Luft Pump, they are well made and designed for outdoors, pricy but they will take the abuse. Otherwie I would buy a Schego. The Schego is easy to repair and get parts for and I have a fair confidence in its construction as well. I would doubt the common HAgen and Tetra units could last long at freezing temps, I think the rubber would fail, theses parts have to be of a higher quality to take such abuse.
