Review on KEDSUM Battery Aquarium Air Pump: Ultra-Quiet Rechargeable Fish Aerator with Dual Outlets - Ideal for Fish Tanks, Outdoor Fishing, Fish Transportation, and Power Outages by Brad Davis

I had originally ordered this product and cancelled as the reviews were unclear as to whether the pump would start up once the power stops. When connected to the power source via USB, once the power stops- the pump turned on as necessary. I had a forewarning on some electrical work being done on my block so had time to plan ahead to ensure my aquariums had the air necessary for the 4 hour window of having no power.