Relatively slow moving, juvenile plane-head filefish Monacanthus hispidus (Monacanthidae) travel along with the algae. They pick off and eat small animals as they move around in the rotating sargassum ball. Adult filefish only grow to be about 11 inches long.
Off the coast of Belize, Smithsonian Marine Science Network postdoctoral fellow, Seabird McKeon, studies floating seaweeds and the minuscule animals that call them home. Check out his slide show and blog and be amazed by the vast array of tiny life forms floating in the world adrift.