Unpleasant power outages happen in the most unexpected times. If you as an owner of an aquarium have a short power outage, you shouldn’t have any major problems given that you frequently and properly take care of the fish tank. But what if the power outage is prolonged? How to Keep Fish Alive during hours-long power outages? Let’s see what you can do!

Water Temperature

The first thing you need to think about is the water temperature. Steady water temperature is a crucial factor in keeping your fish alive. Without electricity, the water temperature can fall/rise quickly because the heater/cooler will be obviously inoperative.

If you need to maintain high levels of temperature, you should close the lid and wrap the aquarium with towels or styrofoam sheets to prevent heat loss. If the room you keep the fish tank in has any type of fireplace, take advantage of it.How to Keep Fish Alive

On the other hand, if you need to keep the tank cool, keep the lids open and float a small amount of ice in the tank. To avoid diluting the salinity of the water, place the ice in a plastic bag. Replace the ice as it melts.


The next thing you should do is maintaining oxygen levels. The best way to do so is to use battery-powered air pumps with airstones. If you already have air-driven filters or airstones installed in the tank, replace the electric air pump with a battery-operated unit. Keep in mind that cooler water can hold larger amounts of dissolved oxygen. Besides, mixing the surface facilitates the exchange of carbon dioxide and oxygen.

Filter Systems

Treating the filter immediately is necessary to preserve the beneficial bacteria on the filter media. You should remove the filter media from the filter as soon as possible and rinse it in aquarium water. Then, put it back in the filter. The conditions within the filter can go anoxic in few hours, which is especially true for closed canister types. The point is that you need to make sure that the filter media isn’t clogged so the bacteria receive the necessary amounts of oxygen.

For short duration power outage the ammonia and nitrite won’t spike rapidly. But if the outage stays longer then we have problem. It would be better if you could run your filters with battery or generator during longer power outage. Otherwise you need to keep changing water every hour to keep ammonia and nitrite level at a tolerable range.

Leave The Fish Alone

In case the power goes out for days or weeks, the best thing to do is leaving the fish alone. Fish also use low amounts of dissolved oxygen in the darkness. Additionally, do not disturb the fish by feeding them. The majority of fish species are capable of living without food for around a week. Another good option would be to ask an aquarium store not affected by the outage to temporarily take your fish until the power comes back on. During such outage if you can’t run your filters you need to keep changing water every hour.

What Can You Do to Prepare for Power Outages?

If you have the budget, you could go for a generator powerful enough to support all the equipment of the aquarium. However, the amount of time a generator can feed the aquarium depends on both the generator capacity as well as the equipment you use. Are you ready to spend money on generators that can keep the power on for days?


What you could and definitely should do however is doing frequent maintenance of your aquarium. If you keep the level of those harmful ammonia, nitrites, as well as the pH level stable, your fish will be able to stay healthy for longer periods of time without power.

Another thing to do is to have spare air-stones, airline tubing, as well as batteries. In general, you need to be able to monitor and maintain the necessary water conditions as long as possible. If the water conditions are taken good care of, you shouldn’t worry too much about the amounts of harmful elements.

You could also keep fewer fish in the tank in the first place! In this case, the decline of dissolved oxygen and the increase of levels of ammonia will be slower.

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