I keep mine in a rack system with 1.2 groups. The tubs I use are relatively small, but it is enough room for a 1.2 group. Anyway mine are all very calm and never nip or bite. The only thing in there tubs is aspen and a piece of PVC for them to chew on. The tubs I use are here:

https://www.schooloutfitters.com/cat...cts_id/PRO4206

Here are some tubs that are a little larger for 1.3 or 1.4 groups.

http://www.webstaurantstore.com/20-x.../70215205.html

I don't think they need cement mixing tubs because they are smaller than regular rats, and I feel that the smaller tubs give them a little more sense of security than the larger ones. Just my opinion. Good luck with what ever you do.

Josh