May not be the most cost efficient way, but you could use submersible fish aquarium tank heaters. You could get something like a 15 watt that is designed for 10 gallon aquariums and turn it down to its lowest level. Could have one in the tank and one in the bowl itself. Would still allow the tank to function as normal - but would probably want to remove the one from the bowl prior to ...... uh .... use. [img]/forums/images/icons/wink.gif[/img]