Food intake, growth and conversion efficiency of two larvivorous fishes have been studied by supplying different proportions of first instarCulex fatigans larvae andTubifex tubifex worms. The worms inhibit the preferential feeding on mosquito larvae byGambusia affinis andPoecilia reticulata. The reduction is more marked inG. affinis than inP. reticulata. Growth and conversion efficiency ofP. reticulata surpassed the values observed forG. affinis indicating that the mosquito larvae are better utilised byP. reticulata than byG. affinis.