It is found in plankton of many species, as well as larger animals such as jellyfish, salps (floating tunicates), and comb jellies.
en.wikipedia.org That said, stomach content studies have revealed they feed mainly upon planktonic crustaceans, squid, and salps, as well as other fish.
en.wikipedia.org Adults likely feed on medusae, siphonophores, ctenophores, and salps, as well as some fishes, crustaceans, and molluscs.
en.wikipedia.org Within the plankton, holoplankton spend their entire life cycle as plankton (e.g. most algae, copepods, salps, and some jellyfish).
en.wikipedia.org But if the phytoplankton is too dense, the salps can clog and sink to the bottom.
en.wikipedia.org