I have also heard of pine being toxic, but not as bad as cedar. Aspen would be a better bet, though, just to be safe. I used loose substrates for a few years, imho they're a waste of time and money (when used for non-burrowing snakes; I do use loose substrate for my frogs and geckos). Now I use all newspaper for snakes. Easy, cheap, safe. And I do have naturalistic enclosures for my BPs, the newspaper looks fine. But, whatever works for you guys.