The main purpose of the research was to develop a smart farm prototype using IoT for high density sea bass farming in closed systems for environmentally friendly and sustainable purposes. This paper presented a water quality monitoring system by using IoT technology for aquaculture (i.e., sea bass culture management in plastic pond). The first experiment (first year) consisted of two parts; first part to design hardware and sensor while the second part to develop mobile application. For water quality sensors under the IoT (Internet of Thing), there were four water quality parameters. These parameters included Dissolved Oxygen (DO), potential hydrogen (pH) level, temperature, and turbidity. The system used sensors, micro controllers, and a mobile application for acquiring and monitoring data. The notification would be sent to users when those parameters were above or below the standard values. The Arduino Nano was used as controller unit to read the analog values from the sensors. Serverless IoTs was created using Firebase Realtime Database (RTDB) and ESP8266. The experiment has been conducted at Faculty of Fisheries Technology and Aquatic Resources, Maejo University. The system was determined and improved to suit the conditions of use in the real area by rearing 9-pond fish for 5 months. The dissolved oxygen was measured every 5 minutes throughout the experiments to reduce the risk in conditions where oxygen levels were below optimal levels, same as other parameters. Mobile application was developed using React Native technology to support both iOS and Android operation system. It can monitor water quality parameters every 5 minutes in real-time. For maintenance the sensor, the sensor probe must be cleaned once a day and a filter cloth must be cleaned every 2-3 days.