oh ok...makes since. I was just told to put it on top of the substrate so it will record the temps that the snake will feel. I usually put at least an inch or two of aspen down, so it seems like not all the heat would make it to the top of the bedding...

Actually i had it that way mainly to calibrate my thermostat...my thermometer is more accurate than the thermostat, so i was making sure to adjust the thermostat to the right temps first.

can see how the snake peeing on the probs would mess things up though. Thanks for the tip!