I have a cool house/snake room due to my A/C. What I did was use two UTH's, and set one up with a T-stat (warm side) then, used a dimmer for the cool side (until I can afford a Johnson T-stat). I also had a problem with ambient temps being too low so, I bought a Hermit crab heater (Zoo-med) that is also plugged in to the T-stat. I affixed the Hermit Crab heater on the back of the tub on the "wall". This type heater is OK to use on plastic, but I would still set it up on your thermostat. This set-up has worked out the best for me temp/humidity wise for my 15 qt tub set-up.