Can You Turn Off A Fish Tank Pump At Night?

If you’ve ever kept an aquarium in your bedroom, you know how annoying the constant whizzing of the air pump can be.

All the sleepless nights and soaring power bills can make you question whether your fish actually need an air pump at night or not. 

So can you turn off a fish tank pump at night? Yes and no. Yes, if your fish tank already has a separately running filter and the water is sufficiently oxygenated. And no, if your filter and air pump are combined, and the water is already oxygen deficient. 

However, there are lots of factors that can impact this decision. And making the right decision is crucial because without oxygen, your fish will die.

 So without further ado, let’s dive into the article!

Can you turn off a fish tank pump at night?

Whether you can turn off a fish tank pump at night or not depends on multiple factors, the most important one being the type of filter you have. The remaining factors include the size of your fish tank, the number of inhabitants, and much more. 

But before we figure out whether turning off an air pump is safe or not, let’s understand the purpose of both an air pump and filter first:

What does an air pump do?

An air pump, also known as a bubbler, is a device whose purpose is to oxygenate a fish tank’s water and expel excess carbon dioxide out of it. The pump creates thousands of bubbles per minute and constantly agitates the aquarium water. As these bubbles rise, they drag gases like carbon dioxide to the surface, and when they pop on the surface, the water absorbs oxygen from the atmosphere. 

So the purpose of an air pump is to aerate the aquarium’s water. Without adequate oxygen, your tank inhabitants would perish. But can turning off your fish tank’s pump for 8 to 10 hours reduce oxygen levels enough to kill your fish? 

For that, let’s understand the purpose of a fish tank filter:

What does a filter do?

An aquarium filter removes excess waste and toxic materials from the water, such as ammonia, nitrates, nitrites. Some filters also remove leftover food and waste products before they turn into ammonia so that your fish tank water doesn’t get too polluted.

Having a filter in your fish tank is compulsory, and turning it off for even a couple of hours can lead to the buildup of toxic materials that can be fatal to fish. However, removing pollutants from your aquarium’s water is much more critical than aerating it. So while it may be possible to switch off your air pump for one night, turning off your filter is totally out of the question.  

But what should you do if your fish tank filters also double as an air pump? Should you turn off your air pump then?

To simplify the answer, here are situations where you can turn off your fish tank air pump at night and conditions in which you shouldn’t:

When you CAN turn off your air pump at night

1. Your filter and air pump are separate

When your filter and air pump are working separately, you can safely switch off your air pump for the night while the filter continues to run. Most filters agitate the water enough to steadily aerate it and maintain oxygen levels. 

This is especially true for external filters and filters that hang over the aquarium. With these filters, the outlet is slightly above the aquarium’s water level. When the water falls back into the fish tank, it creates enough agitation to aerate the tank water and keep oxygen levels constant.

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2. You have a large enough fish tank

The size of your fish tank can significantly impact the oxygen saturation level of the water. In a big tank, a larger surface area of the water faces the atmosphere. This larger surface area makes the gas exchange process easier as the water is able to absorb more oxygen from the air and expel carbon dioxide more quickly.

3. Your tank has few inhabitants

Having fewer tank inhabitants and smaller fish means that there is a lesser need for oxygen. Smaller fish require lesser oxygen compared to larger species. And having fewer tank inhabitants, including plants and other marine animals, means that less oxygen will be consumed in total. That’s why your aquarium’s water can sustain fewer inhabitants for the night without needing extra aeration.

If you have a large fish tank with smaller or fewer fish, it’s a bonus. The more water there is in a tank per inhabitant, the more oxygen each one can consume. 

4. There are other aerators in your tank

Having other sources of aeration is always beneficial while your air pump is turned off. One such aerator is an air stone. These air stones are made out of porous stone or minerals and gradually release bubbles into the water over several weeks.

If you ever turn off your fish tank’s air pump, these air stones can create enough agitation to maintain the water’s oxygen levels. You can place air stones as a backup as well in case your power goes out.

When you CAN’T turn off your air pump at night

1. Your filter and air pump are combined

When your filter and air pump are combined, you don’t have any option but to keep it running. Turning off the water filter for even a couple of hours, even if the water continues to get aerated through some other source, can be deadly. 

It can greatly disrupt the ammonia and nitrate levels of your tank’s water for several days. During this time, the fluctuating water levels can make your fish sick or even kill them.

2. You have a small fish tank

A small fish tank with a limited surface area can significantly limit your aquarium’s oxygen levels, even if there’s sufficient agitation. Because the bubbles will have less surface area to rise and pop, the water will absorb less oxygen from the air. 

A small tank will also have less volume of water in total. So if you have many tank inhabitants, there might not be sufficient oxygen to let all of them breathe.

3. There are lots of inhabitant in your aquarium

When there are too many fish in an aquarium, oxygen deficiency is very likely if the air pump is turned off. There won’t be enough oxygen for all of the inhabitants to breathe, and as a result, most of them will start gasping or even die.

4. You have no other aerators in your aquarium

If you don’t have any backup aerator in your aquarium, such as air stones, the water might become deficient in oxygen. This is particularly true if your tank is small and has too many inhabitants. Oxygen levels will start dipping rapidly and might suffocate your fish.

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Plants are another cause of oxygen deprivation. During the day, they will conduct photosynthesis and oxygenate the water while absorbing carbon dioxide. But during the night, the role is reversed, and plants start absorbing oxygen while expelling carbon dioxide. 

So, if you have lots of aquatic plants in your aquarium, turning off your air pump during nighttime might not be such a good idea.

Ways to identify the oxygen level of your aquarium

Knowing how well-oxygenated your aquarium is can help you confidently switch off your air pump during the night. However, it might also help identify when the water is already oxygen-deprived, and turning off the air pump might not be in your best interest.

The simplest way of testing your aquarium’s oxygen level is to use a digital oxygen meter. This device can provide the most accurate estimate of your water’s oxygen levels. However, digital oxygen meters aren’t the cheapest devices on the market.

Another alternative is a chemical test kit. You can purchase them at your local pet stores, and they will do a great job at giving you a rough estimate of the water’s oxygen level. But the results can sometimes be flawed due to other chemicals present in your aquarium’s water.

If you don’t have access to either, a tool-free method to know whether your tank is properly oxygenated or not is to notice the behavior of your fish. If they constantly swim near the surface and gasp for air, then it’s likely that your aquarium does not have adequate amounts of oxygen.

When your aquarium is already oxygen-deprived, turning off the air pump might not be the best idea. But if the tests indicate that there’s enough oxygen, you can go ahead and switch off your fish tank’s air pump for about 6 to 8 hours.


Can you over oxygenate a fish tank?

Yes, over oxygenation is possible and can be potentially fatal to fish. It can cause gas bubble disease, which causes oxygen bubbles to form inside the fish and appear on their skin, as well as near their eyes.

How long can fish survive without an air pump?

Most fish can only survive up to two days or 48 hours in still water with zero aerators. However, this amount may vary depending on your fish species, the tank’s size, and many other factors.

Will your fish die without a filter?

Fish might begin to die as soon as 12 hours after the filter is turned off depending on the fish tank’s size, water condition, number of inhabitants, and the fish’s health, amongst other factors.

Are fish afraid of bubbles?

It’s possible to scare your fish if your air pump is too loud or pushes out bubbles too violently. Most fish can identify the loud noise and strong flow of bubbles and will start fearing that particular part of the tank.

How can you aerate an aquarium without an air pump?

In case of an emergency, the best way to aerate your aquarium’s water is to fill a pitcher with water and pour it into the fish tank from a height. This agitation will create lots of bubbles and act as an air pump to increase your aquarium’s oxygen level.

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Nadine Oraby

My name is Nadine; I am a passionate writer and a pet lover. People usually call me by the nickname “Joy” because they think that I am a positive and joyful person who is a child at heart. My love for animals triggered me to create this blog. Articles are written by vets, pet experts, and me. Thanks for visiting. Your friend, Nadine!

2 thoughts on “Can You Turn Off A Fish Tank Pump At Night?”

  1. Thanks for sharing this information, I was not aware of many things you have explained. Keep sharing this useful information with us.


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