I have the UTH on the side of the tank, not the underside. But I just removed it until I get my large multi-unit thermostat in a few months. She was doing fine before I put in on anyway. I have realized after trying a few different things that it is definitely the thermometer that is malfunctioning. It continues to read just around 70f no matter where I place it unless it decides to go cooler. Her hiding rock(which is directly parallel to the thermometer) was even warm to my touch, yet it still read under 70f. I will be making a trip to Walmart tomorrow morning to remedy this issue. Thank you to everyone for your responses. That'll teach me to trust analog thermometers in the future!!!