Having water movement and air exchange is key when the power goes out and having a DC-powered backup pump is a good investment. The Aquatop AC/DC-One Aquarium Air Pump is one of the many portable backup oxygen source for your fish tank during an AC power failure or if you’re moving or will have your fish out of your tank for an extended period.
There is an cord that plugs into an outlet, but it doesn’t power the pump. Instead it just detects when the power goes out. When it does, it kicks on the battery power to deliver air to the tank via tubing and an airstone.
The Aquatop AC/DC-One Air Pump comes with a 23 in. air line, air stone, and an AC power failure sensor that automatically switches to battery operation if the power goes out. It does run on a pair of D batteries that you will have to buy separately. MSRP is $21.99 but there can be found for $15 and under online.