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Can You Turn off a Fish Tank Pump at Night? 4 Factors & FAQs

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By Lindsey Stanton

Tropical fish swimming in lighted aquarium or fish tank

The pump in your fish tank is a pretty important thing no doubt. Now, most aquariums do need a pump or air pump of some sort in order to supply the aquarium with enough dissolved oxygen to keep the fish happy and healthy. After all, they do need to breathe, so this is quite important.

However, pumps can be pretty loud, and the larger ones can use a lot of power, so you might be tempted to turn it off, especially during the night. So, can you turn off a fish tank pump at night?

Well, this answer is not really a straightforward yes or no kind of thing, because it really depends on a few different factors. If you have an air pump that is separate from your filter, then yes, you might be able to turn it off at night, but if the air pump’s function relies on the filter being on, or vice versa, then things get a little more difficult.

There are other factors to consider as well. Let’s talk about this issue of turning your aquarium pump off during the night right now.

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Is It A Good Idea To Turn Off Your Air Pump At Night?

The noise from the air pump is really bothering you, or you are worried about the cost of your electricity bill. You are tempted to turn off your air pump at night, yes, that thing which provides dissolved oxygen for your fish to breathe.

Is it a good idea to turn off the fish tank’s pump during the night? It really depends because some pumps are integrated into filters while others are separate, and this is going to be the deciding factor over anything else.

Air Pump Separate From Filter

If you have just a good old air pump that is separate from your aquarium filtration unit, then you should be able to turn it off during the night, at least for a few hours from when you go to bed to when you get up.

As long as your filter is still running and cleaning the appropriate amount of water per hour, this should be fine.

For one, the filtration process itself, both the filtering through media and the expelling of filtered water back into the tank, create air bubbles, air circulation, and oxygenation.

If you turn off your air pump at night, the filtration unit alone should be enough to keep the water supplied with more than enough dissolved oxygen. Keep in mind that the filtration unit does always need to be running to keep ammonia and nitrite levels to a minimum.

Even if the filter did not do such a good job at oxygenating the water, if you have a pretty large tank and not too many fish in it, turn off the air pump for 7 or 8 hours still shouldn’t make too much of a difference.

Filter running or not, there should be enough dissolved oxygen in the water to allow your fish to easily survive overnight.

Air Pump Integrated With The Filter

Now, this is a bit of a different story, one which involves an air pump that relies on the filtration unit in order to run. Whether your fish tank would have enough dissolved oxygen in the water or not really is not the issue here.

If your filter and air pump are connected and run using the same cables or power source, then you cannot turn the air pump off during the night.

Fish are pretty fragile creatures when it comes to water parameters, especially unwanted compounds like ammonia and nitrites. You just cannot turn off your aquarium filter for 8 hours per night, every single day.

In all reality, fish tank filtration units should never be turned off because they are important and very necessary to the well-being of all aquarium inhabitants.

The oxygen is not the issue here; the lack of filtration is.

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The 4 Factors To Keep In Mind Before Turning Off Your Fish Pump

Before you decide whether or not to turn the fish tank pump off during the night, there are some important deciding factors you should keep in mind.

Here is what you need to consider before shutting off an aquarium air pump at night.

1. The Amount & Size Of Fish In The Tank

aquarium with coral, clay pot, cichlids, plants
Image Credit: Frantisek Czanner, Shutterstock

The first thing to consider here is how many fish you have in the fish tank and how large they are, compared to the volume of water in the aquarium.

Simply put, the more fish you have, the more gills there are sucking the oxygen out of the water, and the larger the fish are, the more oxygen they will consume.

So, if you have a really large fish tank and not too many inhabitants, sure, it is probably fine to turn the pump off at night.

However, if you have a lot of fish in a relatively small space, there might not be enough oxygen present to last the night, so in this case, you should leave the air pump on.

2. The Amount & Size Of Plants In The Tank

The next thing you need to consider here is how many plants you have in the tank with your fish and how large these plants are.

Now, it is true that during the day, living plants engage in photosynthesis, thus using up carbon dioxide and supplying the water with fresh oxygen. However, what most people do not know is that this is the opposite during the night.

When plants do not get sun, when it’s dark, they do not engage in photosynthesis, and they actually suck the oxygen out of the water.

Therefore, if you have a lot of plants, big plants, in your aquarium, they might use up too much oxygen and leave your fish with not enough for the night. Moreover, there might also not be enough oxygen for the plants themselves either.

3. The Filtration Unit & Water Agitation

tank bubbles aquarium
Image By: xzgorik, Shutterstock

As we talked about above, the filtration unit also makes a difference, but it does also depend on the type of filter.

For instance, a fully submerged filter is not going to produce nearly as much oxygen as a hang-on back filter with a waterfall cascading off of it.

A filtration unit like a HOB filter will force a good amount of oxygen back into the water as it expels the clean water back into the tank.

If you have a filter like this, you should be fine to turn the pump off during the night, that is if the pump is separate from the filter.

4. Water Temperature

The other thing that you need to consider is the water temperature. Cold water can hold a lot more dissolved oxygen than warm water.

So, the warmer the water, the less oxygen is going to be in it on a consistent basis. Therefore, if you have a really warm tropical tank, one with lots of fish and plants, you might want to think twice about turning the pump off during the night.

However, if you have a cold water tank with limited inhabitants, there will be more oxygen present and more to go around, so you could probably manage to shut the pump off at night without endangering any fish or plants.

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Is There Enough Oxygen In My Aquarium Water?

Well, it is really quite simple. If your fish are at the surface of the water gasping for air, or if they appear to have trouble breathing with gills flaring frantically, you can be sure that there is not enough dissolved oxygen content in the water for your fish to breathe easily.

You can always get a meter to read the level of dissolved oxygen in the water, which will be a great indication of what you should do in terms of turning the pump off at night or leaving it on.

Is It Ok to Turn off the Aquarium Light at Night?

On a related note, people also ask us if it is ok to run off the aquarium light at night. The easy answer to this is yes, absolutely.

In fact, you should turn the aquarium light off during the night. Fish in the wild act and behave according to the solar cycle; in other words, they rely on day and night periods to function properly. It is how they know to sleep at night and get their rest.

If you leave the light on 24 hours a day, your fish is going to get confused, stressed out, and may develop some pretty severe health and behavioral issues.

So yes, not only is it ok to turn off the aquarium light at night, but it is, in fact, necessary to do so.

Just think about living in the arctic where it is sunny, without dark, for 6 months of the year. Would this not mess with your mind and ability to make a daily schedule?

Aquarium cleaning fish tank
Image Credit: Open Mind Art, Shutterstock

How Long Should You Leave A Fish Tank Light On?

This depends on what kind of fish you have and where they originally come from. Realistically, you should try and provide your fish with as much light as they would normally get in the wild in their natural habitat.

If the fish live near the equator, they will get more sunlight, but if they live further north or south on the planet, then they will get a bit less.

Do some research into where your fish comes from and what the light conditions in that area of the world are like.

This should be a good indicator of how long you should leave a fish tank light on for. Usually, something like 14 hours of light and 10 hours of dark should suffice, give or take depending on the fish in question.

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Final Thoughts

There you have it folks, everything you need to keep in mind about whether or not you can turn the aquarium pump off at night. There are a variety of things to consider.

Now, in most cases, you are probably fine to turn off the pump during the night for a few hours. However, if you feel uneasy about it, you are better off being safe than sorry and will probably want to leave it on. Remember—your fish need to breathe too!

Featured Image Credit: Sergio Bertino, Shutterstock

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