Zacro AH476 Submersible Aquarium Heater, Auto Thermostat Fish Tank Heater with Protective Sleeve and Digital Temperature Readout Zacro AH352 Submersible Aquarium Heater is an upgraded version which can control and adjust the temperature automatically. Provides Accurate Thermal Control. Use the inner temperature controller on the top to set and adjust the desired temperature. Safety Protection --- This aquarium heater can automatically control the temperature High efficiency heating performance: adapt the heat pipe which is high heat transfer efficiency; it also adapt precision sensor probe which can control the error within 33.8F. High temperature resistant flame retardant, high efficiency, fast heat transfer and long service life.