I'm going to assume the snowflake behaves itself with hermits and snails and just bothers shrimp so correct me if I'm wrong.
I'd do something along the lines of 15-20 of each: Nassarius, Cerith and Trochus snails, of course you wouldn't have to add all at once. I hate hermits and don't ever recommend them, but you certainly could trim the number of snails and add hermits if you'd like.