Design and Field Evaluation of a Portable IoT-Based Water Quality Monitoring System for Mud Crab Aquaculture

Water quality monitoring is important for maintaining suitable environmental conditions in mud crab (Scylla serrata) aquaculture. Conventional monitoring is commonly performed manually and does not provide continuous observation or automatic data recording when network connectivity is unavailable. This study presents a portable Internet of Things (IoT)-based water quality monitoring system for measuring pH, electrical conductivity (EC), salinity, dissolved oxygen (DO), and temperature. The system employs an Arduino Nano with an ADS1115 16-bit ADC for sensor data acquisition and an ESP32 for wireless communication. Measurement data are displayed locally, transmitted through MQTT to a Node-RED dashboard, and stored on an SD card to support offline data logging. Sensor calibration and system testing were followed by approximately seven hours of field monitoring at the Marana Silvofishery Pond Installation, Maros, South Sulawesi. The field results showed pH values of 7.42–8.07 with an average of 7.76, EC of 39.97–41.25 mS/cm with an average of 40.68 mS/cm, salinity of 27.98–28.88 ppt with an average of 28.48 ppt, DO of 4.75–6.06 mg/L with an average of 5.39 mg/L, and temperature of 28.75–29.81 °C with an average of 29.41 °C. The pH sensor produced an average error of 0.28% during calibration, while the EC sensor produced an error of 0.16% against a 12.88 mS/cm standard solution. The system successfully recorded measurement data in online and offline conditions and displayed the measurements on the monitoring dashboard. The results demonstrate that the developed portable system can support continuous field-oriented water quality monitoring in mud crab aquaculture.