The plankton light reactor is a simple system for producing plankton in a natural food chain. Within the plankton light reactor, micro-algae are produced with light, fertiliser and CO2. The micro-algae can be fed directly to many filter-feeding invertebrates, especially to zooplankton. The growth rate of the micro-algae in the plankton light reactor is enormous. If the supply of light, CO2 and nutrients is continuous, the biomass of the algae may increase four-fold within 24 hours. Both fresh- and saltwater species of phytoplankton can be cultivated.