The best replacement for plankton is krill.

The best alternatives to plankton are rated as following:
★★★★★  krill
★★★★  algae
★★★★  mr krabs
★★★  phytoplankton
★★★  nekton
★★  spongebob
★★  spongebob games
★★  krabs
★  amoeba
  zooplankton
  spongebob squarepants

Your alternative for plankton is not listed? Suggest!
Speaking about plankton, one probably shouldn't forget about krabby patty.

Other search terms related to plankton and their ratings are:
★★★★★ krabby patty
★ spongebob pictures
You have in mind a companion for plankton and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of plankton in all years. Click on graph for more.
plankton
krill
algae