I personally use a 12 watt U.T.H. heater meant for 10-20 gallon terrariums that i placed on the back side center of my 20 gallon terrarium. I also throw over one or two blankets over the whole terrarium when it gets cold, especially at night. As for a thermostat, they say to place those in the coolest area in your terrarium. Hope that helps at all.🙂