I've got a battery powered air pump, length of air hose, and an airstone. Power goes off, this is 'enough' to keep the critters happy and healthy for a few hours.
After a few hours, I've got a generator. The generator will run the main return pump, keep flow and oxygen cycling through the system. Should be good for a good long time this way.
Generator also powers a pellet stove, same room as the tank, to keep temps up in winter. Fans in summer. Refrigerator/freezer, and an extension cord for whatever miscellanious stuff we might need... lamps, charge the cell phone, etc.
You want to be cautious about powering sensitive electronics off of a generator! I would NOT plug your expensive LED lighting, your Apex controller, programmable wavemakers, etc. into the erratic, unbuffered output of your typical home generator.