Plankton plays a very important role in the marine aquarium. Phytoplankton and zooplankton are distinguished which can be grown in a plankton reactor. Phytoplankton is mainly consists of algae and thus constitutes the first stage. It is eaten by zooplankton, so two separate approaches are necessary to achieve the specific breeding. Zooplankton such as brachionus plicatilis spec. or Artemia-Nauplien are necessary for breeding the marine fishes and sea horses larvae in huge quantities. A regular addition ensures a stable and healthy tank biology and nutrition of corals and invertebrates.