Features: This adjustable aquarium heater is suitable for many occasions. The fish market is a common place for us. It can maintain the freshness of fish. They are also suitable for places where aquatic life such as fish tanks, aquariums, and small fish for ponds are kept. You can choose the following power according to the size of your tank:30W/ 50W/ 75W/ 100W . This fish for tank heater automatically turns off if overheating. Power selection: The applicable power of the heating rod is based on the room temperature of 20 degrees. For example, when the room temperature is 20°C, 15L of water with 50W is enough, but when the room temperature is lower than 15°C, more power is required. In addition to room temperature, also consider the heat dissipation conditions and the tightness of the fish for tank. The heating rod does not work: the heating rod has a constant temperature of about 26 degrees, and the temperature cannot be adjusted. If the room temperature or water temperature is 26°C, the heating rod does not work. Some people's body temperature is around 36 degrees. It is not advisable to test whether the heating rod is working by hand. A thermometer is recommended. If the normal water temperature is around 22-27 degrees, the heating rod is working. Specifications: Material: ABS Size: As Shown Power: 30W/50W/75W/100W Input Voltage: 100-240V 50/60Hz Temperature Vontrol: 26±3℃ Power Cord Length: 110cm/43.31in Package Includes: 1x Aquarium Submersible Heater note: 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item.