Undertank heating with aspen bedding - where to put the temp probe

Hi all,
Like most of us, I use undertank heat tape for my hognoses. And, like many/most of us, I have my hognoses in enclosures with a few inches of aspen bedding. I’m trying to dial in my temps a bit and I’m curious where you experienced breeders put your temp probes. Three inches of aspen is a pretty good insulator so on the hot side of the enclosure, the temp can vary quite a bit from the top of the bedding to the bottom. If I want to get the top of the bedding layer to the upper 80s, it means that underneath the bedding, it could be in the upper 90s. If I aim for the bottom of the bedding layer to be in the upper 80s, the top could be in the 70s.

So, again, where do you guys put your temp probes?


Anytime I am using an under tank heater, I place the thermostat probe between the under tank heater and bottom of the tank.

Overhead heating works better in this scenario because if you have a thick layer of bedding the heat may not be able to make it up through, and as you mentioned, can be pretty variable at glass vs on top of the bedding.

I use a ceramic heat emitter and coconut husk bedding (it holds humidity much better) in all of my tanks

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You might be better putting the heat pad on the side or getting a CHE. When using a heat pad the prope always goes in between the pad and the glass.

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As someone who’s doing this right now with a ball python and a thick-ish layer of substrate, I put the probe against the back of the glass of the tank somewhere kinda midway.

But keep in mind you’ll probably have to supplement with a heat source above as well. I use a mat below and then above a heat panel. I noticed my ball was always kinda chilly and would never go to her “warm” side. So added heat panel and now at night, after feeding, and during the winter she’s hanging out over there.

So with my hognose I keep the probe right in the other side of the glass under the substrate. I also set it at about 90 so that his hide stays about 80 or so. If he wants to be warmed he’ll burrow which he typically does not but it’s also not so hot that it will hurt him if he does. I’ve used the same method for my MBK and not had any problems yet.

Safe placement of the probe is between the UTH and tank/tub. There is always a chance the animal could borrow and urinate on the probe, causing the mat to get too hot. If they somehow dislodge it then the same thing would happen.