Yeah, I think the guy at the pet store didn't know what he was talking about. I have the same UTH on one of my tubs and it will EASILY hit 120 if not regulated. At the very least, you need to put that on a dimmer to dial down the amount of current going in. Dimmers work ok if you have the tank in a room with a steady temp. Ideally, you would want a thermostat to keep a constant regulated temp though. With the thermostat, even if your external temps fluctuate, the internal temp will be nice and steady...