i have a thermostat hooked up to the UTH, i had the thermostat maxed at 108 and in tank temps were still low. i think the UTH may be too small. i bought the one for the 10-20 gal tank but it was smaller than i expected it to be. i got the CHE in the hopes i could turn down the UTH a bit so its not running maxed 100% of the time. i have a thermometer with a probe on the hot side and an acurite thermometer with humidity gauge on the cold side. Thermostat probe is between the UTH and the base of the enclosure.