I used to volunteer to water the hanging baskets in my town (they told me there were 48 of them, stretched out over 2 miles after I had done so). I used a reservoir in the back of my pickup and a Rio pump that put out about 1200 GPH. I ran it with a cheap Noma 400W power converter from Canadian Tire ($100). I used it for two hours non-stop and it lasted about 5 days, for a total of about 10 hours.

Modern powerheads and air pumps will last a long time. You could heat the area with a well vented/filtered propane heater if you wanted to save the gas or battery power.

Bought a noma 400 from canadian tire.Power was out for 6 hours,it ran my 500 aquaclear,skimmer,heater and one powerhead,no problems,one thing I like about battery backup is that when the power goes out,it dosen't skip a beat everything keeps running as of the power never went out,well worth the money.

Yeah, UPS (uninterrupted power source) systems have that definite advantage. You can always daisy chain more deep charge batteries to it for extended outages. Once you get into days, rather than hours you have bigger problems than your tank crashing :)

here's a nice UPS, might be a little big but can probably pick up cheap. Well maintained (can trust me on this)

We lost power last winter for over 16 hours. Boy was i happy to have a generator. It may sound like a lot of $ for something you might not need but if you do. You'll be happy you bought one. I would have lost much more than the few hundred bucks the generator cost me.