That is a good thought - he has a heater that is supposed to automatically kick in whenever the temp starts to dip (I think it is the Hydor Theo) but I will make sure to actually check and be sure that the water temp is staying consistent. Right now his tank is placed along an outside-facing wall of our house, so I have actually turned up the heater temp setting to something like 85 in order to get the actual water temp to stay at around 76-78. Maybe I will also try to strategize about whether there is any other location where we could keep him so he's not on an external wall.