Can You Turn Off the Aquarium Filter at Night?

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The filtration system is a vital component of any aquatic setup. The filter preserves water quality by eliminating debris, dirt, organic matter, waste and oxygenate the water at the same time.

Ideally, the filter should work 24/7, but that’s not always the case.

Power outages are still a thing in this day and age, during which the filtration system will be on pause.

You also need to clean it occasionally, typically every 6-8 weeks, depending on the tank’s size, how many fish you have, and the species.

Some fish are messier than others; case and point – cichlids. The cleaning process requires removing the filter, effectively ceasing the filtration effect.

So, if your fish can live without the filter for an hour or 2, can they do so for longer? Can you turn off your aquarium filter overnight?

The answer is no, you can’t, and we’ll discuss in detail why that is.

Why You Should Not Turn Off Aquarium Filter?

There are several overarching reasons why turning off the filtration system is a bad move.

We can understand these better by looking at what the filter does:

  • Mechanical filtration – Simply put, the filter will remove all floating particles that usually consist of dirt, sand from the substrate, dead organic matter, plant residues, food leftovers, etc. All these particles will cloud the water, affecting the tank’s aesthetics and causing discomfort to your fish. Pausing mechanical filtration for a night won’t lead to a disaster, but the following several points will.
  • Biological filtration – Every filter will house colonies of beneficial bacteria that thrive in moist and dark environments. These microorganisms consume ammonia and convert it into nitrites and then nitrates. The latter isn’t as dangerous for your fish, but ammonia is. Pausing biological filtration may result in your fish experiencing ammonia stress and poisoning within hours. They may all be already dead by the time the night is over. There is a higher risk for this to happen in the case of messier fish which can increase ammonia levels fast.
  • Chemical filtration – The nitrifying bacteria will consume ammonia and nitrites, but that’s about it. You need chemical filtration to cleanse the tank water of heavy metals or other, more dangerous chemicals like chlorine or chloramines. Filters based on activated carbon can do that. It’s obviously a bad idea to pause your filter’s chemical filtration every night since this will disrupt the system’s chemical balance.
  • Water oxygenation – The filtration system will improve water oxygenation, which is an essential perk for many fish species. You would be amazed how fast the water oxygen levels can drop during a 7-8 hour pause. Your fish may begin to suffocate and even die as a result. The problem is that, even if that doesn’t happen, pausing the filter regularly will stress your fish due to the repeated episodes of struggling to breathe. And fish stress is the silent killer that all aquarists fear.
  • Cut off water flow – Not all fish require a consistent water flow, but those that do cannot be deprived of it. The water currents created by the filtration system keep some fish more active and provide them with a natural-feeling environment. They also help them breathe better since the water currents force oxygen through the fish’s gills. Pausing the water flow won’t necessarily kill your fish immediately, but it will stress them out. Repeated stress will eventually get to your fish, affect its immune system, and leave it vulnerable to many fish disorders.
  • Temperature regulation – Few people realize this, but the tank’s filtration system improves the effectiveness of the heater. Pausing the filter will create temperature imbalances and fluctuations that will hurt your fish over time. In some cases, it may even send the fish into thermic shock, which is generally deadly.

Based on these aspects, cutting off the filtration system at night is a terrible idea. Sure, fish will react differently depending on the species, but not will rejoice.

And eventually, they will all feel the damaging effects.

How Long Can the Filter Be Switched Off?

It has been observed that the filter’s biofilm starts dying off within 1 to 2 hours after stopping the filter.

This could have potentially fatal consequences for your aquatic life. If the filter remains off for sufficient time, the filter’s biofilm will be completely eradicated.

Sure, the tank also contains its own biofilm since the beneficial bacteria will spread throughout the environment.

They will mostly form colonies in shaded places like inside the substrate or in various decorations like caves, crevices, wood, etc.

But the filter will contain most of these colonies, specifically because they are safe and don’t have contact with the fish or other aquatic creatures.

So, there’s no one to disturb their formations, allowing them to thrive.

Allowing these microorganisms to die will soon affect your tank’s biological filtration.

Ammonia levels will increase dramatically and fast, poisoning your fish and killing off the aquatic life. So, your filter should never remain out of service for more than an hour, preferably.

In the eventuality of an unexpected power outage that will last longer than several hours, you should:

  • Cleanse the filter to remove all trapped debris and dirt that will muster and decompose, affecting the beneficial biofilm
  • Keep the filter submerged in tank water since beneficial bacteria cannot survive without humidity
  • Perform at least one larger water change to dilute any toxins that may have accumulated during the power outage

If you’re in an area with frequent power cuts, I suggest investing in a generator or forgetting about keeping a tank fish altogether.

Frequent power outages will eventually overcome your ability to manage the situation effectively. You will lose your fish shortly; in which case, the efforts are almost never worth the outcome.

Why is My Aquarium Filter Noisy?

Tank filters will produce their fair share of noise, but it shouldn’t be too bothersome.

Today’s filters are more advanced and tend to be quieter than they once were.

That being said, they may still produce excessive noise in some cases, mostly due to:

  • The filter’s type – Some filters are noisier than others. You should consider this point before purchasing your system of choice.
  • The water splashing – This effect relates strictly to the filter’s power and placement. Sometimes, surface water agitation is so messy that it can actually bother some people. In this case, consider lowering the filter’s power output, especially if your fish don’t need that type of water agitation.
  • Clogging issues – The extra noise may also be the result of an unclean filter that requires immediate maintenance. The system will begin to misfire, causing more noise and becoming less productive when clogged with dirt. The same problem happens in case the filter sucks in a rock or other hard material that could even break the system. And even if it doesn’t, the resulting noise may be enough of an issue.

All these problems have simple solutions. Choose your filter carefully and maintain the system adequately in the long run.

Your filter requires more extensive cleaning once every 4-8 weeks, depending on the filter’s type, size, the species of fish, and how dirty the water gets.

How to Make My Aquarium Filter Quieter?

When dealing with a noisy filter, the first thing to do is discover the source.

Based on what you find, the available solutions include:

  • Cleaning the filter – This is the go-to method since accumulated debris or dirt is the most common cause of a noisy filter. Clean the filter thoroughly, put it back in, and listen. If the noise is gone or drastically diminished, you’ve been lucky. If not, there are several other strategies to try out.
  • Adjust the pump – If the source of the noise is water splashing, consider either lowering the flow rate or dropping the hose lower into the water. This will reduce the currents hitting the water surface and causing an exaggerated agitation effect.
  • Inspect and repair the filter or the pump – In some cases, the filter may have faulty parts that have become disjointed and move around the filter’s case. If there’s an easy fix to the issue, you’re in luck. If not, you may need to either have a professional repair it or simply replace the entire piece.

All these tips are only useful in case your filter starts off quiet but gets louder with time. That’s a sign that something’s changing with the system that needs addressing.

But if your filter was loud, to begin with, you may need to upgrade it to a quieter version. There are some recommendations and DIY tips you can try to lower your filter’s decibels, but I would have these with a grain of salt.

You could be messing up the entire system and causing more damage in the process.

Can Fish Survive Overnight Without a Filter?

Yes, most fish will survive overnight without a filter. Some fish species can even survive without any filter at all, like guppies, zebrafish, bettas, ember tetras, and others.

The problem is that you need to work extra hard to make up for the filter’s absence. Since there is no filtration available, your system will only rely on its biofilm to counter ammonia and nitrites.

But this is nowhere near enough since the aquarium is a closed system that functions very differently than an open one. The accumulated ammonia has nowhere to go and will soon overwhelm the tank’s natural biofilm.

To counter that, you need to perform more frequent water changes and remove fish waste and food residues pretty much daily.

This is fine provided you have a lot of time on your hands and are passionate about it, but few people are that passionate.

Not to mention, you won’t be able to perform mechanical or chemical filtration. This means that the water will be dirtier, and your fish will experience a decrease in lifespan and overall life quality.

Get a filter!

Can You Turn Off Air Pump at Night?

Yes, you can turn off the air pump at night, but this is rather circumstantial. If your air pump is part of the filtration system, then turning it off would mean turning the entire system off.

And this is a big no-no based on all the reasons we’ve already discussed. If your air pump is separate, there’s typically no problem with turning it off for several hours during nighttime.

However, not even this aspect works the same all the time. If your tank is rather overcrowded and you have a lot of fish and plants sharing the same space, you may need to keep the pump running.

Plants will produce oxygen during the day, but they will consume it during nighttime and produce carbon dioxide in return.

Having a lot of fish and plants will drain the water oxygen faster. This could cause your fish to experience lower levels of oxygen and become stressed or even suffocate as a result.

So, always be mindful of your setup before deciding whether it’s a good idea to turn off the air pump or not.


The filtration system is a vital component of any closed aquatic setup.

It should be running 24/7 to keep the system stable and ensure optimal filtration and cleaner and more well-oxygenated waters.

It is theoretically possible to keep your fish without any filter at all, but I wouldn’t recommend it.

As you’ve seen, the filter comes with a variety of benefits that you simply can’t ignore.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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