Air and temp
With a power outage you have lost filtration, air exchange and temp control.
First, no food. I'd note tank temps and start a journal so I kept all 4 tanks going in order. Consider treating with Prime or similar for nitrite and ammonia detoxing.
Second, temp control. Wrap tanks if it is cold to retain heat, uncover tanks if it is hot to increase evaporation and cooling. Net uncovered tanks to contain jumpers.
Third, air. Both the tank and the filter require air. Drag a dry net through the tank periodically to add some air. Remove filter cartridges and sink in the tank, open canisters (after sealing inlets). H2O2 is dangerous and can harm fish, so don't use this until really necessary. If you have a battery air pump, add some air to the canister on occasion. If you don't, I would think that by removing some water to a jug and shaking vigorously, then returning that to the tank, you'd add a lot of air to the tank. (shaken, not stirred!)
Last, water changes. It might be wise to draw a lot of water and store in a tub or big bucket for water changes. Some water treatment plants may be down and be required to use harsh chemicals upon restarting certain units, I'm guessing. After the east coast power failure I read of a few individuals who weathered the outage fine but lost fish upon doing a water change.
Planted tanks should have CO2 turned off and sunshine if weather and location permits. Net top if uncovered.
When the power returns, rinse all filter media gently before starting up. Maybe treat again with Prime at startup, monitor paameters.
Power outages, the best reason to be aware of stocking limits!