Hi TFO! I have a question. So tomorrow I am going to OSH to pick up some play sand for my tort. I'm moving him out of a mortar box and into a 40 gallon tank. It's MUCH bigger. I also have an undertank heater as well that' I'm going to use...Well anyway, I have a question about the bedding. I read that most people here use a 50/50 mixture of play sand and dirt, but I want to know why? I have my Greek on sphagnum moss and he seems to be fine with it. Easy to clean, but it is rather dusty and messy when you are cleaning. How thick should the substrate be? He's about 3-4 inches tall. How should the substrate be? Like split or mixed? Thanks fellow terrapin enthusiasts!