Have one of these each in 125 gal tank and 12 gallon NanoCube, to provide backup aeration in event of power failure...
These things are noisy as hell.
With two of them in the living room, the racket they make will easily get anyone out of bed in middle of night if there is a power outage and they go off.
Cheap "insurance" - & a good alarm if power fails at night when sleeping.
Silent Air B11 Air Pump
Life insurance for your fish- the bubbles go ON when the power goes OFF! This battery powered air pump is a must for your precious aquarium fish. The pump automatically turns on when it detects no A.C. electricity, providing your fish with life-saving aeration during a power-outage.
Instructions:
Insert two "D" batteries. Connect air-stone (included) to one end of the flexible tubing (included). Attach other end to pump. Place pump near aquarium and drop air stone into aquarium. Plug unit into electic outlet. This connection allows pump to detect a power outage. The pump will only operate when there is no A.C. electricity. Press "ON" button on side. Pump will now automatically activate in event of power failure. Pump should be tested periodically by unplugging it from outlet. Make certain the button is in the "ON" position when plugged in.
Warranty:
Penn-Plax guarantees your new "Silent Air" Pump against defective parts and workmanship for a period of 90 days from date of purchase.
Availability: Usually ships in 2-3 business days.
$10.99 (aquarium guys)
"Power Out" Alarm 
I was planning to hook up my filters to an old UPS that is currently attached to my PCs. I have to check if this could work... 
