I made it through hurricane Ike with no power for 6 days. Here's some tips..Definitely place blankets (I used three per tank) around the entire tank. Do not feed! they can a week or so w/o food w/ no problems.Feeding will only increase ammonia. If at all possible...do a pwc before the power goes out...if your media is new, it will lessen the effects of dead bacteria entering the system when power returns (if no power to the filter). Also, if you don't have the filter hooked up to the gen., float your biological media in the tank so it doesn't dry out. Understand, you have your furnace, refigerator, tv (for weather updates) all to hook up, so you may not be able to handle a bunch of aquarium hook ups. Your heater is most important as weel as water flow and/or movement. I used a few back up battery bubblers in my SW reef tanks. They worked like a charm, the aeration provided enough O2 to keep all my livestock alive. It would be best if you can hook the filtration up to the gen, but if not...defitely get the battery bubblers ( and at least 10 batteries per back up pump (2 D cells required per pump). The cool thing is, they're automatic. When the power dies, they come on automatically. If you don't do a pwc and media change before the power goes out...do it before it comes back on! This will save the anaerobic bacteria from flooding the tank!
Hope this helps! I lost not one fish, or invert!