i think its better if they hibernate. but to answer the question you can get a 55gal drum, put the heater in it and pump the water into the bottom of the drum. the water will warm up and drain out the top of the drum back into the big tank. the only problem of heating the tank in winter is there is too much variation between the air and water temps which can make them sick. i think they are alright unless the water freezes solid.