Aquatop's Submersible Heater with Dual Digital Display makes monitoring your aquarium temperature simple with reliability and an easy to read visual display. The Dual Digital Display shows you both the current water temperature and the desired temperature you select. Super accurate; the heater will keep your water heated to your desired temperature within +/- 1 degree. Great for fresh or salt water; the heater also comes with the following convenient features: Remote sensor to accurately monitor water temperature Durable suction cups for secure hold High-impact safety glass to avoid breaking Automatic shutoff set at 93 degrees to prevent overheating The 100w D2HT-100 model is 11 in. long and rated for aquariums up to 30 gallons. Internal memory will retain desired setting after a power outage. For more information on heating aquariums; please read our article on Fish Tank Heaters.