Phytoplankton
Unicellular microalgae cultivated as food for filter-feeding corals, bivalves, zooplankton and invertebrate larvae.
Detailed explanation
Phytoplankton (Nannochloropsis, Isochrysis, Tetraselmis) is the basis of the marine food chain. It is easily grown with light, fertiliser and salt water.
In the aquarium it is dosed to feed: filter-feeding corals (Gorgonie, Dendronephthya), bivalves (Tridacna, feather duster worms), copepods and rotifers (which in turn feed the fish).
Commercial products (BioPlankton by Brightwell, Phyto-Feast by Reef Nutrition) are convenient but expensive. Self-cultivation reduces costs to a minimum.
The dosing must be done at night or with the skimmer turned off for 30-60 minutes, otherwise the skimmer removes the phytoplankton before it is consumed.