Mosquitoes cause nuisance to human beings by biting and transmitting vector-borne diseases. Though several control strategies are available for their control, biocontrol holds much promise. Among biocontrol agents, larvivorous fishes are gaining importance. Hence the present study has been undertaken to test the efficiency of O. mossambicus in the larval control of Culex quinquefasciatus. Experiments were designed with different ecological conditions like prey density, volume of water, container shape, presence of vegetation, predator density and time of the day to test the biocontrol potential of the fish. The fish was able to control the third instar larve of C. quinquefasciatus and hence it can be used in mosquito control programmes.