I've been using aspen for several months now with my juveniles. I've had no problem whatsoever. The snakes are healthy, and the water python loves burrowing in it like those things in "Tremors." I admit, it does work better for colubrids, which don't have the humidity requirements that the pythons do, but if you're vigilant in your husbandry you shouldn't have a problem. The aspen in our Durango Mountain Kingsnake's tank only has to be changed when he makes a mess. The aspen in the ball python enclosures get changed once a week. The aspen in the water python's tank gets checked daily. I usually take out the damp aspen every other day and do a full change once a week.