I use Aspen, and it seems to absorb well and the snakes LOVE burrowing through it. The only concern is to make sure you stay on top of the cleaning even when it doesn't look like you need it. The aspen absorbs a lot and gets dirty even though it still looks like it is pretty clean. On average I'd say once a month, change it all out completely (depending on the size of the snake and cage, I guess that could vary)