Hmmm. I use the recommended Hydrofarm thermostat. Is it possible that I just don't have a good enough seal on the tank? I know the instructions for the UTH say to "stick to the tank and not have any air bubbles" for the best heat transfer, but that is not possible to do with the big chunky thermostat probe in between the UTH and the glass. Around the probe is sealed to the glass well, but obviously the area the probe is sitting is not touching the glass. Could that be causing some descrepancy in the heating?

I have only had it for a day or two here, so I'm still fiddling with it during the day to find the sweet spot.

Could it be that it gets too cold in my room at night (It's a pretty segnificant drop) for the thermostat to heat the hot spot? The thermostat is set to cap out at 95, because that keeps the hot spot at about 92. But if it's significantly colder in the surrounding area, wouldn't it be harder to keep the substrate warm? The thermostat can cap out and be a nice 95 degrees, but since it is so much cooler in the room, that 95 is not enough to keep the hot spot as hot as it should be. Kind of how in regards to ambient temps, my CHE is enough to keep it at the perfect temp during the day, but at night it gets cold enough that it can't heat it up to the proper temp? (With the UTH it can, but this was the day before I got the thermostat).

I'm having a hard time getting what I'm thinking into words, does the above make sense at all? I don't want to raise the cap on the thermostat, because then during the day the hot spot would get too hot.