A series of assessment on the predation effectiveness of rice fish (Aplocheilus latipes) and freshwater planarian (Dugesia japonica) by the influence of different temperature, salinity and pH concentrations were conducted against house mosquitoes (Culex pipiens pallens) larvae during the period of September, 1994∼Apri1, 1995. The most effective predation by both predators was shown at 25$^{circ}C$； Aplocheilus latipes consumed on the average of 78.2 larvae/day followed by 62.0/day at 30$^{circ}C$；Dugesia consumed 3.7 larvae/day by mature individual followed by 1.5/day by intermediate individual. Both predators died above 35$^{circ}C$. Rice fishes showed higher predation at 55 consuming 82.7 larvae /day than that of control (69.0/day) while the planaria showed lower predation rate of 1.8 larvae/dy (Mature) at 0.4％ than that of control (3.7/day) with tendency of an inversely proportional to the salinity increase up to 1.2％. Aplocheilus fish survived at pH concentrations of 5.0∼9.0, however, 50% mortality of fish were derived either from strong acidity of lower than 4.0 pH or form strong alkalinity of over 10.0 pH concentrations. Further biological control potentiality of the agents in their application was elaborated.