Shimp/crayfish "living" in the swirl filter will stir the solids, keeping the solids in the water column and defeat the purpose of having the swirl filter. The purpose of a swirl filter is to have solids settle at the bottom where they can be removed on occasion.
I am not an expert. My system is only about 13 months old.
thanks for the reply. i figured as much. just thought maybe since they feed on fish waste, it would lessen/eliminate the physically remove waste on occasion part.
thats awesom, i havent even started yet