The probe for the thermostat goes between the heat mat and tank on the outside of the tank. Someone link a pic please lol. And you can keep your dimmer on the highest output but still needs to be regulated. Probes should not be in substrate since your snek can move it, pee on it, poop on it or get stuck on however your keeping the probe in place. Nothing sticky ever goes into the tank. Welcome to the newbs club. We have all been here. Lol