I have kept gerbils in a 30" long tank, with soil as substrate, and they did not smell. they burrowed and nested and had young...
I know you are talking about rats. but are gerbils close enough.....
It does seem like a natural alternative, but each to their own.

I know you are talking about rats. but are gerbils close enough.....
It does seem like a natural alternative, but each to their own.