Hello, I have been using wood pellets on mine for a very long time. I was using cat litter for the first few months but besides it being bad for them, it was EXPENSIVE. I think that my ferrets enjoy wood pellets better, I didn't have any trouble switching them over, they were used to them already. When I first got them, I didn't have a supplier of wood pellets, that's partially why I was using cat litter. I haven't knowen of any kinds that are bad. Advice on using would just be that it basically needs to be emptied out every day, especailly now that I've added 2 more ferrets to my other 2. I never thought I'd have to change it everyday. My ferrets could go without any mess for a couple of days before I'd have to change it. Speaking of, after this email, I need to be changing litter. I have to share with my dad and his 7 ferts. But I'd say that one 40 lbs. bag would last our 11 ferts probably, a couple of weeks. But we get 40 lbs. bags for $3.00 a pop so it's not that bad at all. I think the only way it would go 'bad' is if it got damp in anyway. In that case, it would crumble and would not useable for ferret litter. Since we live in such a small town in Iowa, we don't need to stock up. We just go the the place that makes wood pellets for burning stoves and have had no problems with not being able to get any when we need it. Obviously Iowa isn't in the NE, but just so you know. Hope I could be of help. I also wanted to make a comment on the boy-girl issue. When I got my first 2, I LOVED my male George, he was about 7 months old. He was PAST adorable, and he was my BUDDY. Then I started to fall in love with my clam, sometimes nippy female. But when it comes down to it, the boys have GREAT personalites. I love ALL sexes, but in ferrets, it's gotta be boys! Alison~ Geroge, Grizzly, (new additions) Brandy and Tazz Ken and Doreen~ Doc, Laser, Stevie, Johnnie, Dannie, K.D. and Quest [Posted in FML issue 3944]