Depending on the tank size and water quality,I have read that the tank will be OK for up to 5 hours before you should start to worry. I have seen O2 tablets that you drop into the water. I think they work kinda like alka seltser,as far as the bubbles.I saw them at a bait and tackle shop to keep live bait alive. As for filteration,I guess you could do water changes,and probably wouldn't hurt to stir the water around every so often. They also sell battery powered air pumps.And you can get those power inverters that you hook up to a car battery and run the whole tank. Thats about all I can think of,other than to say NOW is the time to start thinking about what you are going to do if this happens. Because when the whole town goes black,your pretty much screwed.