Submerge probe into fish tank to measure water temperature (Submerge probe only, do not submerge thermometer in water). Easy to apply suction cup and easy to read lcd screen; temperature readings to within 1 degree Large, easy to read lcd display; compact design for discrete use Temperature range -50 degree Celsius ~ + 70 degree Celsius; Operating temperature -10 degree Celsius ~ +50 degree Celsius. Powered by one lr44 button cell (included)