I use both. I have them both on themostats. The UTH is set to 90 and I have the lamp set to "warm." The lamp turns on and off throughout the day while the UTH stays on most of the time, unless the probe reads that its getting too hot. I also worried about ambient temps. I keep four different thermometers on my snakes tank. One on the warm side, one on the cool side, one really low, inside, closer to the ground, since that's where he spends most of his time and another near the inside and top of the tank. Ambient temps near bottom and top usually only range a 1-3 degrees, if that. Depends on the weather around here too, Kansas can be hot as humid af one day and a few hours later be cold and rainy.