Juwel Digital Thermometer, comes complete with Battery and Sucker With the large, easy-to-read digital display of the JUWEL Digital Thermometer, you can easily keep an eye on the temperature in your aquarium.The digital thermometer battery has a relatively long life of up to a year. The JUWEL Digital thermometer is suitable for use in both freshwater and saltwater aquariums. Suitable for fresh and saltwater Submerged operation & more accurate than others Measures 16°Cto 42°C (+/-1°C) Clear digital display gives constant aquarium temperature read