Sadly, they are not controlled. I need to buy a thermostat and get that going. For now I have the tub on a shelf and am using wood blocks to elevate it up from the heat pads. So logically one side is higher than the other making the temp grade. It looks silly as hell but I'm getting really consistant temps! Oh I should mention I do have temp/hum probes (good ones) right on the bottom of the tub for the best reading. This guy did his homework, ha!