Hey,

The pic is deceiving. The probe is taped to the plastic above the UTH (which is on the outside). The out temp is the probe and the In is the ambient.

Also, it the substrate looks deeper than it is as the outside corners of the viv are deeper than the middle. THe middle has about 1/2-3/4 while the outside perimeter (where the plastic sinks about 1/2 of an inch) has about 1 inch of substrate.