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How to Care for Your Aquarium Fish During a Power Outage

Bad weather or maintenance by the power company can cause a loss of electricity and send fishkeepers into a panic. A lot of aquarium equipment — like the heater, filter, light, and CO2 system — all runs on electricity, and some of them are vital for keeping your aquatic animals alive. Plus, most of the time we have no idea how long the power outage will last, which unfortunately makes it harder to know what appropriate actions we should take. At Aquarium Co-Op, we’ve had a lot of experience with trying to keep thousands of fish alive when a power outage hits our fish store. Our best advice is to keep calm and create a battle plan.

downed power line

During power outages, keep calm and don’t do anything rash with your fish tanks.

Keeping Enough Oxygen in the Water

In the first 1-2 hours, do nothing to the aquariums. Don’t feed the fish, and turn off any automatic fish food feeders. Also, don’t change any water. In the wild, there are temperature fluctuations from morning to night and fish are built to adapt to them. What they don’t react well to is when humans make sudden changes like dumping in a lot of flakes or pouring in boiling water. Instead, use the time to locate your backup power sources in case you need to hunker down for the long run. This can include:

  • Extra batteries
  • USB battery backup
  • Laptop (to charge USB devices)
  • Large power bank (used for camping)
  • Power inverter for a car battery
  • Universal power supply (or UPS)
  • Portable generator (for long-term power outages)

After 8 hours or more, run some oxygen in the aquarium for 1 hour and repeat this step every 8 hours. (Note: If you have aquariums that are heavily stocked with large numbers of fish or notice that your fish are gasping for air, then you may need to add oxygen earlier and increase the frequency of how often you turn on the air. For example, you may need to run oxygen every 4 hours for an overstocked African cichlid tank.) Use an air stone or sponge filter to create bubbles at the surface, encourage gas exchange, and quickly oxygenate the water. Both of these devices are driven by an air pump, which requires electricity to operate. If you have a USB air pump, you can plug it into a USB backup battery or laptop for power.

An even better solution is to get our air pump with an integrated battery backup. When it’s plugged in, it works normally like any other air pump and the built-in lithium-ion battery continually stays charged. As soon as the air pump loses power, the battery backup automatically turns on, even if you’re not home, and can last for 8 continuous hours. If you are at home, you can manually switch it to Power Save mode. This causes the air to cycle between 15 seconds on and 15 seconds off, thus conserving the battery so it can run for 16 hours or more. This pump has an adjustable air flow as well, so reduce the air flow to further extend the operational time.

Aquarium Co-Op air pump with battery backup

Aquarium Co-Op air pump with battery backup

Finally, if you have an entire fish room of aquariums running on a linear air piston, you can run it on a large camping power bank or an inverter for your car battery. If they run out of juice, you can drive to a friend’s house and charge the power bank while eating dinner together. In cases where the power outage will continue for several days, it may be worth the hassle of setting up a portable gasoline or propane generator for the long haul.

The issue with hang-on-back (HOB) and canister filters is that the filter media compartment does not hold a lot of water or oxygen. To prevent the beneficial bacteria in the filter from running out of oxygen, some hobbyists remove the filter media and place it in the aquarium itself, which holds greater amounts of dissolved oxygen in the water. Another good idea is to completely unplug the HOB and canister filters. Otherwise, all the rotting organics and dead bacteria in the filter media will flush into the tank as soon as the power comes on.

portable generator

Portable generator

Managing the Temperature

In cases where the temperature outside is colder than the tropical temperatures of your fish tanks, we are focused on keeping the fish warm enough until the aquarium heaters are operational again. If you have a few tanks, then consider using packaging tape to adhere heat packs to the outside (not inside) of the aquariums. Shipping heat packs require oxygen in order to produce heat, so only tape the two ends of the heat pack and try to leave most of the surface uncovered. We recommend using one heat pack for every 20–30 gallons of water and adjusting the number of heat packs as needed. Also, the heat packs usually have a time rating for how long they should last, so don’t forget to replace them once they run out of heat.

Another method to minimize heat loss is to put a tight-fitting lid on the aquarium and wrap the whole tank with blankets, towels, or emergency Mylar blankets. By using multiple layers, the air between the blankets will help insulate and prevent heat from escaping as quickly. Large tanks may be too big to cover, but fortunately, greater volumes of water do not change temperature as easily. If you have an entire fish room of aquariums, it may be easier to heat the entire space via non-electrical means, such as a propane heater or wood-burning stove.

Some hobbyists try to keep the water warm by boiling water and adding it to the aquarium. Just make sure not to pour it directly into the tank or else you may scald the fish. Instead, remove some of the tank water into a bucket and mix in a little boiling water. You can use a thermometer to make sure it’s the right temperature before pouring the warmed water back into the tank.

800-gallon aquarium with no power

Our 800-gallon aquarium retained heat for quite a long time during the last power outage.

In cases where the weather outside is very hot and you are struggling to keep the tank water cool enough, try to move the aquarium to a cooler area that is out of direct sunlight or down in the basement.  If you have a portable fan that can run on batteries or a backup power source, blow air across the water surface of the tank to lower the temperature with evaporative cooling. Some hobbyists will float frozen water bottles in the tank to cool down the water, but the ice tends to melt very quickly and can cause drastic temperature changes, which may stress out the fish.

After the Power Comes On

Once the electricity turns on again, do not feed the fish for 24 hours. We want to let the biological filtration (e.g., beneficial bacteria and live plants) catch up with consuming the nitrogen waste that developed during the power outage. In fact, the tank water may even become a bit cloudy if too much nitrogen waste built up and/or some of the beneficial bacteria died during the outage. Test the water for ammonia and nitrite, and if the measurements are above 0 ppm, then do water changes to remove the excess waste chemicals. Finally, clean your HOB and canister filters to remove any dead bacteria and buildup of nitrogen waste before plugging them back in.

In our experience, the longer we’ve been in the aquarium hobby, the longer we feel comfortable not doing anything during power outages, especially in the first few hours. If you want greater peace of mind the next time you lose power, get the Aquarium Co-Op air pump with the built-in battery backup that will automatically turn on and keep the tank water well-oxygenated.

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