What would be the best solution if the electricty went for a few hours??
How would the bacteria and fish cope?
What can you do to keep them alive?

first either a battery powered air pump or oxygen tablets this will keep oxygen in the water, which will help bacteria and fish. battery powered prefared

rap the tank in a blanket this is to keep the temp up. if the power is off to long an empty battle filled with hot water will help this, this water should be changed regulary

I am sure others will be able to help you out more
mickey

There are big debates on how long the good bacteria can survive before dying when oxygen and heat go. Regarding bacteria: Some say 4 hours, some say over 24 hours before you see ammonia spiking. You can take measures to try and avoid problems. Wrap a blanket around the tank to keep heat in. If you have external filters with primers you can pump some water through every half hour, but ideally have a battery powered air pump that you can move between tanks and filters. I had a power cut recently, but it was short - only four hours - so didn't have to worry too much and nobody died.

Oh, all my suggestions were already mentioned...