I would stay away from anything that sifts sand (ie sand sifting stars, orange spot gobies, etc), as it will severely deplete your sand infauna population. Instead, I would recommend getting some cerith and nassarius snails... they will help keep the sand clean without damaging the infauna. Fighting conchs are also good...
"Expecting the world to treat you fairly because you are a good person is a little like expecting the bull not to attack you because you are a vegetarian." - Dennis Wholey