Source : WordNet®

bottom feeder
     n 1: an opportunist who profits from the misfortunes of others
     2: a scavenger that feeds low on the food chain
     3: a fish that feeds on the bottom of a body of water

Source : Free On-Line Dictionary of Computing

bottom feeder
     
        Synonym for {slopsucker}, derived from the fishermen's and
        naturalists' term for finny creatures who subsist on the
        primordial ooze.
     
        [{Jargon File}]