UTH not hot enough on inside of tub?

[Maymay]

Oh, I see. 100F is still fairly high and 85F is decent for the basking spot but could be a bit warmer. Is this the probe of the thermometer? They generally don't measure the direct heat either but the ambient.

Yes, it is pretty high which is why wish the heat would translate to the bottom of the tub so I didn't have to turn it up so much! There is two probes, one from the thermostat taped to the bottom of the uth to regulate it's temp. The other one is a thermometer probe measuring the temp of the bottom of the tub on the inside, the basking spot. So you're saying this one may pick up the ambient temperature more than give an accurate reading of the actual basking temp, which is why it seems cold on the inside?