With the ever-changing nature of technology and the vigorous development of artificial intelligence, traditional fishery has gradually transformed into smart aquaculture. The current smart sensing instruments on the market can accurately measure water quality parameters for fish farms, but they are too expensive to be used popularly. On the basis of the mobile application developed by Taijiang Agriculture Biotechnology, a local company of Taiwan, and our empirical cumulative trend, we propose a smart technology for monitoring water quality in fish farms using a cellphone camera sensor. By the proposed method, we captured and recorded the RGB values of the water color using a cellphone camera sensor. At the same time, we measured the water quality parameters using a spectrophotometer and a Secchi disk at four fish farms. As a result of experimental design and analysis, we found an obvious correlation between water color and various water quality parameters. In the future, we expect to achieve the target that fishermen can use a cellphone to obtain real-time water quality information by utilizing the proposed low-cost and efficient aquaculture technology.