well, I believe the sticky guages are crap. I use the digital ones which also measure hot and cool side temps. It's called acu-rite(they should sponsor this site from all the endorsement). Now about your humidity being too low in a tub, well do you have a water bowl in their, cause where ever it is the humidity will be well above 30%, and you will have to soder some holes around the tub due to the humidity being too high. Also, what kind of tub are you using?? And yes, Aspen bedding does hold moisture. hope this helps