The phenomenon of increasing and decreasing the temperature of the water will cause the fish find it difficult to make the process of mobilizing the energy and the fish will die in a very quick time, causing losses for the fish cultivation. Automatic control system at the fish hatchery pond will be very useful to assist fish cultivation keep the water temperature at the hatchery pond fish have always remained stable at a predetermined threshold. Using a mini computer that Raspberry Pi 3 model B as processing, a temperature sensor DS18B20 as the temperature gauge and relay as the water pump and heater controller. The system automatically heats the water when the temperature is less than the limit set temperature and the system automatically cools the water when the temperature exceeds the specified temperature limits. Determination of temperature and temperature monitoring accessed through a browser on laptop and smartphone by accessing the IP Raspberry Pi have connected to the same network with laptops and smartphones.