Temporary clean-up crews...
Tim (G. smithii) gets a collection of nassarius, astrea, cerith and sometimes stomatella, at least once a month. Any hitchhiker crabs (pretty or not) and all hermit crabs (though he doesn't like the taste of them - or maybe they are too much work for too little food).
When live treats run low he gets dry shrimp pellets, frozen krill or reef mix (variety is the spice of life after all).