What to Do for Your Fish Tank During & After a Power Outage

During a power outage, acting swiftly can help your fish survive until the power comes back on.

Published September 21, 2023
girl testing the water of an aquairum

Your power can go out at any time, and it’s understandable that you worry about your fish tank when it does. Depending on what type of tank you have, your aquatic critters probably rely on a water filter, pump, heater, and lights. Fortunately, your fish can probably survive for about two hours without electricity, but you’ll still need to act quickly. Here’s what you need to know about your fish tank during a power outage.

Time Is of the Essence

A fish tank is usually safe for close to two hours without power, but this time frame really depends on a few factors.

  • Number of fish. More fish means the oxygen levels in your tank will be depleted more quickly.
  • Fish types. Some fish species are resilient and won’t be impacted by fluctuations for a short period, whereas others are incredibly fragile and could be affected immediately.
  • Ambient temperature. If the ambient temperature outside is cold, chances are your fish tank will cool down faster.
  • Aquarium needs. How many electrically powered devices does your aquarium rely on? Greater needs mean your time will run out more quickly.
Quick Tip

Back-up generators or battery-operated pumps and heaters are always the best way to help your tank through a power outage. But if you don’t have these items ready, there are plenty of other ways you can help your fish.

Keep Your Fish Safe During a Power Outage

If you know your power will be out for less than two hours, it should be fine to do nothing during the outage. Interference could actually have a more harmful effect on your fish than letting them ride it out for a short period. But if you’re approaching that two-hour mark with no power in sight, or if your fish show signs of distress, you’ll want to take action.


Unfortunately, it’s possible for fish to suffocate if there’s not enough oxygen in the water. The single most important thing you can do for your fish tank during a power outage is keep the water aerated. To do this manually, follow these steps.

  1. Using a clean, large pitcher or vessel, scoop some water out of the tank.
  2. Pour it back into the tank, making sure to do so from about 6 inches (15 centimeters) above the water’s surface. Do this a few times.
  3. Repeat this process every 15 minutes until the power comes back on.


Most fish need to live in water between 75° and 80°F (25° to 27°C), which is pretty darn warm. Monitor the tank’s temperature frequently to keep the water from cooling down or warming up too rapidly.

If the power goes out during the cold months, you’ll need to take action to keep the water from cooling down. Immediately wrap a blanket around the aquarium to help it retain heat. You may need to float water bottles filled with warm water to keep the temperature up.

If the ambient temperature in your house is high, you can float water bottles with cool or frozen water to keep the temp down. This is also important if you have an axolotl or another aquatic critter that lives in a cooler temperature.


Without a filter, harmful compounds can build up in the water. To keep this to a minimum, don’t feed your fish while the power is out and avoid feeding them for about 24 hours after the power comes back on to keep the bio load down. If you test the water and detect high levels of ammonia, you can carefully perform a 25% water change.


Most fish can survive several days without light, so it isn't necessary to worry about lighting. Keeping the water oxygenated and at the right temperature should be your priorities.

Quick Tip

If it's safe to do so, you may want to safely evacuate with your fish tank to a location with power. 

Prepare for Power Outages

If you live in an area where power outages are a common occurrence, it’s wise to prepare well in advance. Get a battery-powered filter, heater, etc., as a reliable source of backup power to keep your aquarium safe. But in a pinch, swift action and elbow grease can help you get through a power outage.

Trending on LoveToKnow
What to Do for Your Fish Tank During & After a Power Outage