Yesterday, I talked about keeping the temperature steady in an aquarium during a power outage.
Fish also need oxygen in their water and oxygen comes from water movement. In my aquariums, I have air wands that provide a curtain of bubbles along the back wall of the tank. During a power outage, those air wands are still - which means oxygen is depleted very rapidly.
If you find your fish hovering at the top of the water surface gasping, it means they need more oxygen.
There are at least two ways you can keep the water moving and aerated.
If you don't have battery powered aerators, any movement will create air bubbles, oxygenating the water. Yesterday I mentioned poking small holes in a gallon water jug and allowing the water to drip into the tank. This will also have the effect of oxygenating the water. If temperature is not fluctuating, you can use a gallon of water out of the tank itself; getting the jug filled up creates air movement in the water. Then the steady drip on the surface of the water will keep the water oxygenated.
Tomorrow: keeping fish waste to a minimum.