Rotifers, especially Brachionus sp. constitute an important link in the food chain of inland water bodies. Brachionus calyciflorus out of the different species of Brachionus, is recognized by The Society of Environmental Toxicology and Chemistry (SETAC) as a potent bioassay organism in aquatic system. B. calyciflorus is considerably pollution tolerant species and can endure high levels of organic nutrients. The presence of B. calyciflorus, in relation to hydrological parameters is an indicator of aquatic eutrophication. Brachionus calyciflorus can thus be favoured as ‘test organism’ in aquatic toxicology because of its sensitivity to most toxicants and thus can also be used in ‘bio-monitoring programs’ for water quality assessment in the wetlands and also in water reservoirs.