As for the UTH thermostat probe I failed to mention have it mounted outside the tank between the glass and the UTH as mentioned above and have a probe on top the surface of the substrate (I use moss mats and terrarium liners) and offset the UTH thermostat to give you your temp at the surface. For example my thermostat is set at 93 for my UTH and i get 88-90 at the surface of my substrate. I don't use shavings so my little girl don't come into direct contact with the hot glass underneath.