I had a thermostat in the substrate on top of the heat pad, but that is all. And no it is not on a dimmer. is on 24 full power. This leaves the actual air tank temp around 70-80, it depends, but surface temp on cold side high 70s, low 80s, which hot surface temp is the high 80s, low 90s.I think that if anything the cold side maybe a little cold, but he loves sitting on the hide on the cold side, and never goes onto the hot side. not sure why. if i put it on a dimmer id be afraid that the temps would drop much to low. when i get back home, i will get exact temp measurements from exact locations. It all depends on where the digital probe is located and where the heat lamp is located. Where should i put each for the most important results?