Digital aquarium thermometer displays water temperatures from 0-37°C in 0.1°C increments. The pre-alarm flashes when the temperature drops below 18°C or exceeds 28°C. To install: Insert the battery, remove the protective film, then simply stick the thermometer and press it onto the outside of the clean aquarium glass. The 4-part Velcro adhesive makes it easy to remove the thermometer at any time. Accuracy: +/- 1.0°C. Battery: 1 x AG10. Size: 5 x 3.5 cm. Number height: 1.8 cm - easy to read. Do not immerse the thermometer in water! The water temperature is transmitted with high accuracy through the aquarium glass to the temperature sensor at the back of the thermometer.