In the nearly 20 years that I've been an aquarist, I have experienced only two significant power outages that affected my tanks. Two nights ago I thought might be the third. A massive oak tree fell across the road perfectly perpendicular to the power lines along the street, snapping three power poles and bringing to a halt a whole host of services (electricity, cable television, and cable Internet). Being certain the outage would be through the night, I unpacked my brand new battery powered air pumps and hooked them up to the tanks. Fortunately, the outage was only for three hours (our utility company is phenomenal). However, the new pumps worked flawlessly.
For more information on emergency plans, see my post from March titled Be prepared, not sorry.
There are several brands of battery powered air pumps available. Because it's almost inevitable that you will need them eventually, I encourage you to acquire some. Look for features that best fit your needs - some can operate on either one or two batteries, some require two batteries, some are battery/AC combinations that auto switch to battery when AC ceases.
I use the Bubble Box portables by Marine Metal Products. These come with short silicone tubing, an airstone, and a weight to keep the stone submerged. All three components come stored in the battery compartment (batteries are not included) as shown in right image above. They run on either one or two D-size batteries and claim two batteries supply nearly 40 hours of run time.
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