Safety guarantee: The explosion-proof quartz glass shell is double sealed, explosion-proof and anti-corrosion. Prevent your fish or turtle from being hurt by touching the heater.Low usable water level: The aquarium heater can be used with a 3.5cm water heater, designed for fish and turtles.EXTERNAL CONTROLLER AND BUILT-IN THERMOMETER: The external touch controller makes it easy to adjust the temperature and change units without getting your hands wet. The LED digital display clearly and accurately shows the real-time water temperature. Overheat protection: It will automatically turn off when overheated, and the aquarium heater is equipped with intelligent constant temperature heating, multifunctional, providing a safer and more comfortable environment for your fish.NOTE: The aquarium heater should be completely immersed in water. Never leave the water. The heating rod must be completely submerged in water to turn on.