I like to use natural dirt/sand/decomposed granite, even a layer of straw as it's soft and absorbent. All of these need to be changed frequently, every day or every other day, depending on soilage. You want to keep the habitat or compound as clean as you can to avoid any upper respiratory issues. I've used rabbit pellets as well, in case they want to eat the substrat, but this can get pricey as it would need to be changed every other day because the pellets mold rather quickly, especially in warm climates or a warm habitat. Depending on the size and age of the youngsters, I also use surgical drapes, (folded or cut to size) or sheets & towels but not terry as the torts feet can get caught in the loops. These can be changed and washed so easily so really time savers. Another thing I like to use is indoor/outdoor carpet, the no-nap type. You can buy it at Lowes any size you want and it's very reasonable. The biggest plus is that I can put a clean piece in their compound and take the soiled outside to hose down, dry and R & R. A lot depends on your habitat size (NOT glass or an aquarium!) and whether it's indoor or out. Just some examples to make husbandry (housekeeping) easier for the caregivers.