A couple of Nassarius snails would be good, I would not recommend anything larger than that in a nano. Make sure you have a good water flow, you may need a second pump.
I used to stir the sand myself with a stick about the size of a pencil or a plastic ruler about once a week. I would put a bit of filter floss in the overflow first, stir stuff up a bit and then remove the dirty floss when things had settled.