TetraT Submersible Heater is designed to keep your aquatic fish comfortable, with an electronic thermostat that automatically maintains a consistent water temperature of 78 degrees and prevents overheating, extending heater life. An indicator light lets you know when the water is heating (red light) and when it reaches the proper temperature (green light). Inside, silicon carbide crystals improve heat distribution and transfer. The strong glass tube is heat and shock resistant. This submersible heater is easy to use - just attach to the inside of the aquarium wall using the suction cup (included) in an area with good water circulation. The Tetra HT Submersible Heater is available in different wattages to fit your aquarium: use the 50-watt HT10 in 2 to 10 gallon aquariums; 100-watt HT30 for 10 to 30 gallons; 150-watt HT40 for 30 to 40 gallons; and 200-watt HT55 for 40 to 55 gallons. This heater is UL Listed. Since 1951, Tetra has developed the worldàmost comprehensive body of fish food knowledge, and fishkeeping enthusiasts have looked to the brand for products and solutions that add ease and beauty to their home. Whether you're an experienced hobbyist or just starting out, Tetra has everything you need - from a large variety of quality fish food and innovative equipment to test kits and decor.