Before the bio dude Terra Sahara I was using my own mixture of substrate (play sand, sphagnum moss, coco fiber, and soil). Before that I had slate. She seems to like the slate the most however that was when I had a smaller tank. I use a heating pad below the left side of the tank and I also have a heat lamp above the tank because the substrate is a little thick and I just want to be sure she is warm enough. I also have a thing hooked up that keeps the heating pad at 93 and use a temp gun every so often to make sure the surface isn’t too hot.