What to Do in A Power Outage as A Fish Keeper & How to Prevent Problems!

fish care fish health

If you look at your aquarium set-up what do you see? A lot of electrical wires that run on electricity! These wires are the life support system for your fish. 

If you live on the coast then power outages are something you are probably familiar with! Sometimes these outages last longer than a few hours, which can cause problems for your fish. 

If you have never experienced a power outage in your area, do not be fooled - they can happen to anyone, anywhere,  trust me!

Your approach will depend on how many fish you have, how big the aquarium is, and what type of power outage has happened. 

Lucky for you, we have put together an article that will help you if you ever do experience a power outage!

Types of Power Outages

Different power outages will affect your aquarium in different ways and determine what approach needs to be taken. 

Localised Power Outage: 

  • Occurs when the main power source that is connected to your aquarium is disrupted, failed, or the plug has become disconnected from the wall.

  • Plug the cable back into your socket and check the circuit breaker. Sometimes it is as easy as flicking the trip-switch back on. 

Generalised Power Outage:

  • Occurs when power lines have come down or a bad storm - these can last a few hours or even days.

  • Unplug anything that could surge when the electric comes back on and follow the step-by-step guide below.


When the power goes out, your fish will shortly be starved of oxygen as it begins to drop. Like us, fish exhale carbon dioxide. As carbon dioxide increases the pH will start to decrease. Reduced oxygen levels can also cause a spike in ammonia levels. The more fish you have, the faster the ammonia levels will increase. 

Using a battery-powered air pump with an airstone can temporarily stabilise the oxygen levels until the power comes back on.


When the power goes out, it can be difficult to control the temperature of the aquarium water. Temperature fluctuations cause stress and can be fatal to your fish. All your heating equipment requires electricity, which becomes useless in a power outage.

Depending on the room temperature your aquarium is it depends on how you act. You may need to retain the heat if you have a cold room or cool the water down if you live in a humid environment. 

To Retain Heat:

  • Keep the lid closed if you have one.
  • Cover your tank with blankets/towels.
  • Smaller tanks will lose heat faster than larger ones!
  • If you have a gas or wood-burner fireplace in the room, use this to your advantage.

To Decrease the Temperature:

  • Open any lids or covers on the tank.
  • Float a few ice cubes in the water - place ice cubes in a plastic bag so the water does not mix with the aquarium water when it melts. When it melts, replace the ice cubes. 

What to do in a Power Outage: A Step-by-Step Guide 

  1. You want to get that filter up and running again. Firstly, empty the filter and give it a rinse - this eliminates any bad bacteria being pumped back into the tank when the power comes back on. 

  1. Prime the filter and return the media into it.

  1. Plug the filter back in. 

  1. Depending on how long the power was out, you will want to perform a 50% water change and always test the temperature, ammonia, pH, nitrite, and nitrate levels. 

  1. It is recommended to wait 24 hours before you start feeding your fish again, and feed small amounts if the water parameters are still not in the normal range.

  1. Monitor the fish’s behaviour and look for signs of illness - unfortunately, ich is common after power outages, so prepare for possible medication. 

  1. Finally, wait it out. If it does last longer than a week, see if you can find someone to temporarily house them or ask your favourite fish shop if they can have them until your power comes back on. 

If you follow these 7 steps, your fish should have a fighting chance of surviving the power outage!

What Can You Use to Prevent Problems During a Power Outage?

The best thing is to buy an emergency generator to power your house up again. This is not only beneficial for your fish but also you - you won't have to sit in the dark or scramble around your house to find candles!

They unfortunately are not cheap but if you have multiple aquarium setups then this is highly recommended. 

The next best thing would be to use battery-powered equipment to control oxygen, temperature, and filtration. Battery-powered air pumps and airstones are important to continue cycling your aquarium.

An uninterrupted power supply (UPS) automatically kicks in when the power cuts out. You can connect essential equipment such as heaters, lights, and filters. These are great to have if you frequently leave the house - if a power outage happens when you are not home, it will automatically turn on. 

If you do not have any of the above, you can manually pump air into the water. 

Use a cup/small container and fill it with the tank water. Pour it back into the aquarium to create bubbles and water movement.

Extra Tips

  • Have spare batteries, extra airstones, and water testing kits handy.

  • If you are out when a power outage happens, perform a large water change to remove any toxins that may have built up. 

  • Avoid feeding during the power outage, as any excess food and waste they produce will create poor water quality - generally aquarium fish can go 3-5 days without food. 

  • If you get a heads-up that you will have a power outage, prepare with a 50% water change before you get a black-out. 

Final Notes 

Power outages can occur at any time, so you should be ready to tackle the problem if it does happen.

Power outages can become problematic, but it does not mean your fish will all die. If you are prepared and follow the steps in this article you can keep your fish safe!

Don’t forget to join our “Help & Advice” support group on Facebook. We offer FREE support from a qualified marine biologist!

Thank you for reading. We hope to see you soon, have a ‘fintastic’ day!

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