These tough, shatter-proof heaters boast smart electronic technology for long-lasting performance. Rugged heater construction enhanced with LED indicator allows fast and accurate confirmation of heater activity. Translucent temperature dial glows red when heating and glows green when aquarium water temperature is at or above set temperature. Internal mesh heating element allows efficient heat distribution while epoxy fill protects against shock and breakage. Helpful safety feature shuts down heater when exposed out of water and restarts automatically when submerged. 1 degrees Fahrenheit accuracy. Marineland Stealth Pro-Heaters are for submersible use in fresh or saltwater aquariums. 10W Mini is factory set to 78 degrees Fahrenheit-no adjustments needed.