I live in Montreal, and its COLD here now, its been below freezing for about a week... My apt is heated but before they turned on the heat back in October, we were having cold nights.
My solution to this has been to keep a 75watt UV bulb (incandescent black light) right on top of the bowl pretty much all the time, positioned in one of those long armed desk lamps.
I also keep a tinfoil that I pierced with several little holes and fitted on top of the bowl most of the time to prevent leap of faith when Im not around and to help slow the heat loss off the surface and keep a buffer of warmer humid air for the little guy to breathe.
Needless to say, fishy is still with me and presently my apt is warm enough with the heat now going that I can keep the light off and it still stays around 78 in the water unless my thermometer is lying. If it gets really cold this winter (like last year when the rads could be melting but with -20 F outside it still cut through!), the UV lamp will come into play again. It definately radiates enough heat that if you leave it there idefinately it should be fine. You just have to watch it a bit to see how close to the bowl it needs to be to reach the desired temp. It may look a bit freakish, but I dont think anymore so than a heating pad or blanket
If I find that for some reason the temperature is fluctuating wildly over the winter, I'll have to go for a 2.5g aquarium and a nano filter and mini heater...
Dont forget if you heat the bowl water, u gotta have water u change it for at the same temp... I was boiling a small amount of water and adding it to the aged to accomplish this when my apt was not warm enough. Now that my heat is going, the aged water is the same temp anyway...
Phew that was a mouthful!
![S :S :S](/images/smilies/ipb/wacko.png)
Hope it helps, and yeah, I know its only workable for up to a few bowls.