Temperature gradient question in a tub setup

Hello,

I am setting up a couple of tubs in anticipation of acquiring a couple of ball pythons. I'm trying to get everything setup appropriately prior to getting the snakes.

The plan is to get newly hatched baby ball pythons that will have about 3 feedings.

I have a 16 quart sterilite tubs with locking handles. I have it sitting on top of a 12 x 18 x 3/4 sheet of Melamine which I adhered a Zoo Med Repti-Therm Mini heater rated for 1-5 gallon tank. The UTH is adhered so that the end with the cord is about 1.5" from one end of the Melamine sheet. So basically the UTH runs "parallel" to the melamine sheet. The tub then sits on top of this UTH with the end of the tub butting up against the "bump" of the UTH that has all the electrical connections. In this fashion the UTH extends a little more than ~ 1/3 of the way into the length of the tub and since it is long ways, it doesn't fully cover the tub's width, I'd guess it covers over 1/2 of the width though (it runs down the middle with a little of the tub overhanging on each side)

The tub itself has holes approximately 1/4" in diameter spaced 2" apart along both long sides of the tub about 1" down from the top.

The entire thing sits inside a cabinet so the top of the 16 quart tub is with about 1/8" of the shelf above it so it basically acts like a rack "top" without actually being a rack.

I have two inexpensive Zilla digital thermometers with the probes. One is placed on the "warm side", on the tub right above the UTH. The other is on the "cool side" on the end away from the UTH on the bottom.

The "warm side" currently reads 92.3 degrees F and the cool side reads 77.5 degrees F.

The cheap dial hygrometer is currently reading just over 60%

Problem is that it doesn't seem like I can get the "cool side" above 78 degrees F. I am currently running the UTH through a rheostat (thermostat is on order) but even when I let it CRANK, the warm side hit 111.1 degrees F and the cool side was still just at 78.5 degrees F.

I'm worried with winter coming and fluctuations in temperatures throughout the day that the "cool" side will get too cold. Also the ambient air temperature seems to be tracking more with the cool side i.e. in the 78 Degree Range even when the probe is placed in the middle of the tub about 1/2 way up the tub wall.

Is my UTH too small for this tub? It doesn't quite cover 1/3 of the tub's floor surface but it comes close. Since I'm getting hatchlings, should I get 6 qt tubs to put over this UTH? Should I replace the $20 UTH with the next larger UTH? Can I just insulate the tubs better so that it holds heat better? Is 77.5 degrees warm enough and I should just stop worrying?

I tend to be long winded so I apologize for the wordy post.

Thanks in advance.

I'm no expert on tubs so if anyone says otherwise listen to them :P First off I'll recommend a better thermometer. I switched to an accurite from the zilla and there was a temp difference of 3 degrees. Accurites are pretty cheap at walmart but I found min online for $11 apiece.

My opinion is that insulating the tubs without extending the air holes to the insulation is going to cause a rise in humidity. Depending on where you live this may not be much but if you're in the south like me it could be a lot. I'm guessing you have a UTH rated for 20 gal aquariums, this is fine for a tub that size and perhaps edging toward the big side. Smaller tubs are an option but if it was me I'd just get another UTH set at a lower temp for the cool side. This way you only have two items to get (better thermometer & UTH) rather than three.

Good luck with the tubs, I'm a recent convert and will never go back to aquariums for my BPs.