Aqueon submersible aquarium heaters are made from thermal shatter resistant quartz glass and designed to absorb impacts, making them extremely durable. An electronic thermostat stops heating once set temperature is reached. A power indicator light turns on when the unit is heating and is equipped with a 6-foot power cord. UL approved, the heater is also programmed to turn itself off when not properly submersed to avoid overheating and damage. This heater can be positioned at a vertical or horizontal angle and used in freshwater and saltwater aquariums. Wattage heaters are available in 50W, 100W, 150W, 200W and 300W. Aqueon products offers a wide range of items so that you can build and maintain a healthy aquatic environment. All the essentials from fish tanks, filters, lighting, food, care, and other supplies that your pet fish needs. We make it easy for you to get your first aquarium and to grow in the hobby as you become more of a fish expert with every step you take and every new thing you learn. Fully submersible, auto shut-off when overheats, resets when cools down. Electronic thermostat stops heating once set temperature is reached. Precise temperature setting adjustable to 1? F (68-88? F). Shatter-resistant Led light turns on when aquarium water is being heated, automatic safety shut off and overheat protection. For freshwater and saltwater aquariums up to 20 gallons.