the most common refered reference to "clean up crew" is in the marine trade of Hermit crabs, cleaner shrimps and other crustation varieties. but they do not eat fish waste! fish waste is just the rubish the fish dosent need, no animal eats somthing that has had most of the nutrience sucked outa it. "only example i can see is dung beatles and flies. Though adult dungbeatles themselves do not eat it, they lay their eggs in it and their larve eat it."