Thermostat will regulate the temps of a certain device. But you really should have a stable ambient temp to start with. I keep my bp's in a controlled air and heated room. Its kept 80-82 during the day and might drop to 78 over night. I also use a UTH for the hot side set for 91-93*. I dont use a heat lamp at all. I put its hide over the hot side and it creates a heated hide for it to go into. Having a hide over the hot side allows the heat from the UTH to get trapped inside creating a higher ambient temp inside the hide.