I am checking out the APC battery backup to solve this problem.
The one I'm checking out is the BE650G, cost about $60 in Circuit City. You can check out the run time chart in the link below:
http://apc.com/products/runtime_for_...m?upsfamily=21
Since I'm running a Hydor#4 pump at 12 watts, it's probably going to last me about over an hour. If the power outage is over a couple of hours, then your best bet will be a bigger power backup unit or an electric generator.