Definitely clean those canisters! Several days will result in some really foul water inside. I would make sure to unplug them so they don't push that water into the aquariums when the power comes back on.
You can also use a battery powered air pump to keep the water in the tanks fresh while you wait out the power restoration.
You can also use a battery powered air pump to keep the water in the tanks fresh while you wait out the power restoration.