I've been using paper towels as substrate for my RETFs because it's the only thing delicate enough to conduct the heat from my (weak ***) Zoo Med UTH.

But lately the humidity is not staying up, even with consistently moist paper towels. What can I use on the bottom of the tank that won't interfere with the UTH?

I've tried using heat mats on the side of the tank but it hardly makes a difference in temperature.

Suggestions? Is there a way to incorporate moss or some other item without blocking the heat? Or should I just give up and buy a stronger UTH? Different brand maybe?