I've reviewed the care sheets and the FAQs and have been lurking around the forums here for a month or two, but I still am confused as to how best to regulate temperatures.

I have two normal ball pythons. Both are males. One weighs about 1,179 grams, and the other weighs 1,068 grams (weights were as of a month ago). I have each ball python in his own 40 gallon glass tank (Zilla Critter Cage). I'm using ZooMed ReptiBark as a substrate, about 1/2 - 3/4" in each tank. Each tank has two Reptile Basics hides (learned about those hides while lurking here and ordered four of them); one hide is on each of the ends of the tank. I also have a small ceramic water bowl in each tank that is changed every other day (if not daily).

One tank is in a hallway between my kids' bedrooms (where the thermostat that controls the heat and A/C in their bedrooms is). The other tank is in one of the kids' bedrooms. I live in Phoenix, Arizona, so during the summer we keep the house at 80-82 degrees for most of day, though we might lower the temperature to 78-79 in the evenings when we are home from work and school (never lower than 78 in the summer months). During the winter, we keep the household temperatures around 68, though sometimes we'll get it up to 70-72, especially in early evening/night (around the kids' bedtimes).

We got the first BP last August, when it was still pretty warm in Phoenix. Thus, we started out using just a 100-watt red light on one side of the tank (might have been 75 watt--I can't recall for certain). That seemed to work very well while the room temperature was in the 78-82 range. However, as winter set it, I had trouble keeping the temperature in the tank warm enough. Long story short, I ended up putting a medium ZooMed UTH under each tank (actually, one tank as a UTH on the side of the tank and another underneath the tank on the same side of the tank, but that's another story--I now am using just the UTHs under the tank and have unplugged the one on the side). In addition, I replaced the red lights with a 150 watt CHE, with the CHE being placed on the other side of each tank opposite the UTH because the UTH didn't seem to be driving up the ambient air temperature in the far side of the tank high enough (I don't recall how high it got, but it was not more than 80, which I thought was too cold).

When I use a Black & Decker infrared thermometer to measure the substrate temperature over the UTHs, I get really high readings (over 110 in some places, but as low as 84 in others--all over the UTH area, mind you). However, when I touch the substrate that is over the UTH, it doesn't feel nearly that warm. Moreover, the Exto-Terra digital thermometers I have at substrate level near the UTHs read 84.6 or so. The Exto-Terra digital thermometers at substrate level under the CHEs have been reading 85-89 this week (depending upon when I check them). Both BPs seem to be hanging out in the hides under the CHEs and not in the hides over the UTHs (though I have, at times, seen them in the hides over the UTHs).

At this point, I am totally confused as to where I should be measuring temperatures (substrate level or higher up in the tank) and which side of the tank I should consider to be the hot spot and which side should be the cool spot. I've got two ZooMed ReptiTemp 500R units that I can use (right now, I have one hooked up to the CHE in one of the tanks, but I am wondering if I should use them for the UTHs instead). I also have a ZooMed Hygrotherm that I am using with the CHE in the second tank (again, should I instead use it to control the UTH instead?). If I use the thermostats to control the UTHs, do I put the thermostat probes at substrate level directly over the UTH (and, if so, how do I do that without it getting in the BP's way?). FWIW, I also have two 100 watt CHEs that I'm not using (they weren't strong enough to get the ambient temperatures up).

Had I seen this site before I bought the ReptiTemp 500R unites and the Hygrotherm, I probably would have passed on those and bought Herpstats. However, I now have a bunch of $ invested in the ZooMed products and would prefer not to spend additional $ if I don't have to. So, with this in mind, do you have any recommendations as to how best to set up the tanks given the equipment I have? Also, where do I want to be measure the temperatures (substrate level, mid-tank, or top of the tank)? I truly appreciate any advice you experts can offer. I'm feeling pretty dumb right now. The only consolation is that both BPs seem to be healthy, though one hasn't eaten since the end of October.