The hot temperature comes from the infrared heater which has a dial for controlling the temp. The UTH has no way of regulating but I use about an inch and a half of aspen on the tank floor so when I place my hand on the substrate over the UTH I can feel the warmth but it's not too hot. She likes to go here after she eats to digest. I use analog thermometers on both sides of my tank but I am considering moving to digital since they're more accurate.