These newly designed Finnex digital glass heaters are fully submersible & can be used in both fresh and marine aquariums. The red LED digital display allows users to visibly read current temperatures in the tank. A single control button allows easy temperature settings, hassle free. Unit uses an ultimate designed internal temperature controller to keep aquarium temperatures steady. Built in with automatic shut off overheat protection at 93°F, our 2mm quartz glass thick tubes one of the strongest glass heaters out there. To further separate this glass heater from the rest, this heaters is equipped with memory, meaning after power outages, at start up the heater will resume your preset temperature settings.