Uninterruptible Power Supply.
It looks like a power strip/surge protector except a bit bigger, and its pretty much a battery. It stays connected to the outlet all the time, and once the power fails it switches over to the battery. You can plug the necessary air pumps, just air pumps as you can use the same one for more than one tank. Try keeping the big energy consuming things off their, heaters and pumps for sumps. You can also invest in some nicer ones and just plug everything in, but be prepared to spend in the hundreds of dollars.