S.T. International Aquarium Thermostat with Double Digital Display, 1000-Watt Most advanced light emitting diode (LED) is utilized to display settings and current temperature Alarm will sound when the water temperature fluctuates by + or - 3 degrees Fahrenheit Temperature controlled circuit is activated by a micro-processor which has an accuracy of + or  1 F Thermostat will maintain any programmed aquarium water temperature from 68 F - 95 F (20 C - 35 C) Automatic alarm sensor and automatic heater shut-off if water temperature changes beyond the range of + or - 3 F and higher than 96.8 F (36 C)