Aspen bedding or newspaper.

[Evenstar]

You just dont want to use cedar.

Or pine. The oils can irritate the skin or even be toxic. But aspen and cypress are totally safe.

I use both paper and aspen. I would choose paper any day, but my Dumeril's boa needs to burrow. Aspen is nice for a week or two, then it starts to get nasty (even with spot cleaning) it works fine of you are using an overhead heat source like a heat lamp, CHE, or RHP. But if you are using a UTH it really can become a pain since it doesn't transfer heat very well.

I so agree! I use disposable cage liners in my tubs and I'll never go back. Like Aaron, I'd only use aspen now if I had a snake that needed to burrow. I use shredded tree fern as a substrate for my GTP's natural viv, but it's a pain to clean. It's worth it for one center piece of beauty, but I'll stick to the cage liners for everyone else, lol....

But as far as aspen or cypress, both are safe and perfectly fine to use!