Monitoring water quality in freshwater pond fish farming is an important thing to do because the quality of the fish depends on the conditions of the aquatic environment in which it lives. Terrible water conditions can interfere with fish activities and can cause mass mortality that will reduce the productivity of freshwater fish farming farmers. Temperature, pH level, and turbidity of fish pond water are measured parameters that represent optimal water quality. This research contributes to developing water quality monitoring instruments that can produce continuous and real-time quality data. The monitoring system of fish pond water quality was designed by installing a temperature sensor, pH sensor, and turbidity sensor. The value obtained from the sensor measurement is then processed using a microcontroller. The system design uses the ESP32 wireless module. It makes an application on Android so that the measurement results from the sensors are used to display integrated monitoring results online as an implementation of the Internet of Things. Then the system can be accessed through an application on a smartphone to show notifications and replace water automatically. And the result of a validity test with calibrators obtained each uncertainty result from the turbidity sensor, temperature sensor, and also the pH sensor is 1.24; 0.136; 0.31 (acid pH);0.2 (alkaline pH). The result of validation testing shows a small uncertainty, that can also understand as to how close the measurement result is to the actual value.