Yeah, you need a thermostat for the UTH. They don't do much for ambient temps, they're meant to provide belly heat. But if they're unregulated they can get to 120 degrees easily and cause burns. For some reason BPs don't realize when they're being burned so they don't move off the heat fast enough. If you don't want to spend too much, you can get a Hydrofarm seedling thermostat from Amazon for around $30. That's what I'm using, so far so good.