I use these battery operated air pumps that turn on automatically when the power goes out. Already came in handy this year when I was out of town during our annual power vault maintenance in my building which shuts down power overnight. I have a heavy bioload and would have lost fish without the pump. Came home without any losses. I use it at least once a year during our electric vault maintenance.
http://www.amazon.com/Silent-Series-.../dp/B000256502