The aim of this study was to investigate the median lethal concentration (LC50) of six chemotherapeutants on silver perch (Bidyanus bidyanus) under two controlled temperatures, 20 and 30 °C. The suitability of commonly recommended concentrations of agents was also examined for silver perch. When the water temperature was 20 °C with 96 h of exposure, the results showed that the LC50 values of malachite green, methylene blue, copper sulfate, formalin, potassium permanganate, and masoten were 0.25, 22.75, 2.12, 112.81, 2.13, and 2.91 ppm, respectively. When the temperature was 30 °C, their LC50 values were 0.21, 5.80, 1.07, 84.71, 1.97, and 0.92 ppm, respectively. This indicated that the agents were more toxic to the fish at 30 °C than at 20 °C. The relative toxicity of malachite green was stronger than the other agents, while formalin appeared to be less toxic than the others. The results also showed that the commonly recommended concentration of 100 ppm masoten for 1 h and 3~5 ppm potassium permanganate for long-term exposure are not suitable for silver perch. Moreover, the exposure duration of 250 ppm formalin for silver perch should be less than 1 h at 30 °C.