Continuous cultures, i.e. chemostats with an continuous dilution rate, are model ecosystems for the study of general regulation principles in plankton communities. Further to an introduction, general continuous culture methods and especially the characteristics of rotifer continuousculture systems are presented. Sections on metabolism and energetics in chemostats, growth models, competition and predator-prey interactions, as well as the application of rotifer continuous cultures to ecotoxicology and their use in aquaculture are included.