The Penn-Plax Silent Air B11 is an battery powered air pump that will turn on when the power goes off. It is a great automatic back-up system that ensures that your fish will stay alive during power outages or when the power goes out. It will turn on when it detects there is no AC electricity, providing your fish with life-saving aeration. Also acts great as an portable air pump.
Pump requires two "D" batteries for operation. AC plug on pump is for power detection only, does not operate pump, or charge batteries. Check battery power regularly by unplugging pump with the pump in "on" position. Pump can operate up to 48 hrs, depending upon battery quality, and operating conditions.