Keeping track of your aquarium's temperature and protecting against unsafe temperatures has neven been easier with JW's® SmartTemp Thermometer. The unique design of the JW Aquarium SmartTemp Thermometer allows you to place the thermometer anywhere on the glass inside of your tank and secure it with the magnet on the outside of the tank with no suction cups required. Features a Green Safe Zone, which indicates the optimal termperature range that shows the ideal temperature range for most tropical fish. The large, easy to read numbers are in both Centigrade and Fahrenheit. Measures 5.5 inches tall.