They can live OK with or without a heater. They originate from waterways around the white cloud mountains in China where it can get very cold. I have had them in ponds year round in Christchurch even with ice on the top in winter. They are easier to convert from hot to cold than cold to hot. You just turn the heater off and get them used to the new water in the pond and they are away. To go back to hot takes a few days.