Jellyfish are considered plankton. The term plankton comes from the Greek planktos, meaning wanderer or drifter. Plankton are considered to be any organisms which cannot swim against a current. read more
To be classified as plankton, size also matters. Jellyfish is too big to be classified as plankton. At least it is too big to be caught in a plankton net. Another point is no plankters consume fish, which some jellyfish does. A third point is no plankters carry toxin to kill its prey. read more