Hello, and to BP.net.

When using an Under Tank Heater, I strongly recommend using a thermostat, or at least a rheostat/dimmer. You should be reading your warm side tempertures under the substrate, over the UTH. This is the hottest temp that your snake can come into contact with. If you are using paper towels or news paper, snakes can find ways to get under it when they want to, and if you are using a wood substrate such as aspen or cypress, snakes will push it aside as they move around in their hides. Unregulated UTH's can easily reach 110F or more. Also, if you are using one of the wood substrates, and the layer is too thick, it will almost act like an insulator, and the heat will build up under it. For these types of substrate, the layer should only be about 1/2 an inch thick over the UTH.