ive measured the warm side and the cool side with a temp gun and an ambient air temp gauge just to be sure it wasnt a false reading, im using a herpstat nd with the probe on the heat tape and its set at 95. my ambient temps are 77-78 cool side 80-82 warm side. the temps really arent fluctuating that much maybe a degree or so. i figured a foot of 11' wide heat tape would be enough for a 41qt tub especially using belly heat