kitty litter tubs in wooden racks...they chew on the water valves but not as bad as the rats...you need tubs that are smooth no edges to chew...follow the RDR link on page one and find his youtube rat rack vids...my racks are the same as his...
1 male to 4 or 5 females...never mix adult gerbs...all baby's go into a community tub to mix blood lines...a large cement tub in a different rack...