Douglas Fir Bark

Burrow-friendly bark for tropical/forest habitats
Reptiles from a variety of habitats...from the tropics to northern forests...will thrive in additive-free Douglas Fir bark. Loose and light enough to encourage natural burrowing behavior, this material promotes the free transfer of heat and moisture essential for the health of cold-blooded pets. Made of 100% natural ingredients harvested in the USA, and readily biodegrade in a backyard compost at the end of its useful life.

Thats what i use. Great Stuff, sorta soft and pourous. I keep an extra bag for when i spot clean. And every month i sanitize the tank and replace with a new bag!