Coconut fiber/Wood Chips/Reptichip etc..... ive never used anything but Kraft/Butcher Paper myself. But I just looked back and see that it is a 20 gallon you’re using so any kind of overhead heat like a CHE /Lamp is going to ddry the-heck out of it. I have a tank that I use for quarantine and I put a heat mat underneath the tank where the water bowl is making the water evaporate and that certainly helps. Went from 45% to 58-60%.
You didn’t say how you were heating i dont think.
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