There is a lot of different info out on these guys, I think because they are relatively new to the pet trade. Aspen is definitely the best thing to keep them in. It's easy and they can make burrows, which the love to do. They have a really hard time shedding in sand, it's too dry and I guess they don't really like sand, they like to burrow. I'm sure in the wild they can find sand/mud to make burrows in, but our sand isn't made for burrowing.
As far as tanks go, I've always heard 10 gallons is perfectly fine for the life of the animal.