I have a 2X6 C&C cage with 4 female guinea pigs. I started out with Aspen, but it didn't control odor at all even when I spot cleaned it daily. I tried fleece but am fed up with it. The fleece didn't seem to wick properly even after 5 washes (and no fabric softener) used. I also couldn't stand seeing all the poop all over the top of it. I sweep it up, and within an hour it's covered again. Right now I have yesterday's news in the cage, but I'm worried that it's going to be too rough on their feet (not sure though - opinions?). I haven't tried pine because I've read that even kiln dried pine isn't safe for them. I thought about trying pelleted pine underneath aspen, but the only brand I can find around here is Equine Pine, and I've been reading on here that people have been having issues with that too, and that it also might not be safe because of the pine smell. I'm also trying to find something relatively cheap since my cage is so large. Any input is appreciated, thanks!