HeaterThis Fish Tank Heater should be 100% submerged into water, Ideal for small glass or acrylic desktop aquariums up 1 to 6 Gallons, not suitable for less than 1 gallon tank. Quick and Easy Installation:Vertical or horizontal placement using, Aquarium heater automatic temperature control 78, no need to adjust temperature, easy to operate, fishes happy. How it Works: Plug in, red light turns on, the heater will start working until water temperature up to 78F, and red light off, then the green light will turn on, heater stop working and keeping constant temperature 78F. Accuracy3F Note: Do not operate or leave product plugged in when your water tank is out of water, heater should be fully submerged into water. It is better to install a water pump to help water circulating while heating.