Eric is an aquarium enthusiast with over two decades of experience caring for a wide array of tropical fish.
Can You Turn Your Filter Off at Night?
It is not a good idea to turn off your aquarium filter every night. The filter plays a key role in the health of your tank, and shutting it down for hours at a time can eventually lead to problems.
Why You Should Leave Your Filter On
Of course, you probably know that the filter removes debris such as uneaten and decaying food, fish waste, and dead plant matter from your water. Getting that junk out of there is vital, but it is only one of the important duties performed by your filter.
They Support Good Bacteria and Aerate the Water
Did you know that colonies of bacteria live in your tank, and they convert toxic chemicals in the water to safe chemicals? This is known as the nitrogen cycle.
There are two reasons your filter is a key part of this process. First, the filter is one of the main places in your tank where those microbe colonies thrive. Second, your filter helps to aerate the water. Oxygen is very important in your tank, not only for the fish but also for the microbes. Without it, they would perish.
New aquarium keepers often install an air pump to create bubbles in their tanks, believing they are adding oxygen to the water. It will add a little oxygen, and it usually doesn’t hurt, but a good filter will circulate the water enough to provide all the oxygen your fish require. If you turn off your filter, so that the water is no longer flowing over the elements inside, you deprive the microbes that live there of the oxygen essential for their survival.
Like your fish, the microbes in your tank are pretty hardy. Turning off the filter for a night now and then isn’t going to hurt them much. But if you do it every night you are depriving your fish and the microbes of oxygen for eight hours out of every twenty-four, and that will eventually catch up with them.
Turning Them Off and On May Make Your Tank Dirtier
The final reason not to turn off your aquarium filter at night has to do with what happens when you turn it back on. Depending on how recently you’ve cleaned them, some filters will regurgitate a mess of dirty water and debris back into your tank during the priming process.
If you go through that every morning you are basically dumping all the garbage your filter removed from the tank the day before right back in. This is not only a good argument for keeping your filter running, but also for keeping up with good tank maintenance practices.
How to Reduce Aquarium Filter Noise
If you are thinking of shutting off your aquarium filter at night I’ll give you the benefit of the doubt and assume it isn’t because you want to provide some kind of sadistic survival challenge for your fish. Instead, I am going to guess it is because your filter is too noisy. There are a few things you can do about that.
You'll want to figure out if the noise is due to water movement or the filter mechanics itself. If it seems to be water movement, check the water level in your aquarium. Low water levels can cause a waterfall effect and an increase in gurgling noises.
With most filters, you will want your water level right up to the lip of the filter outlet (be careful not to overflow your tank, of course). This allows water to gently flow out without a lot of turbulence. Some filters have an adjustment knob that lets you change the flow rate, which can help reduce noise.
Sometimes the noise is caused by the filter components themselves. Most filters can be taken apart and cleaned. Sometimes gunk builds up on the impeller, or the impeller itself becomes damaged, causing a rattling noise. Sometimes gunk prevents the plastic tube pieces from fitting together properly or joining with the impeller section properly. This can cause a rattling or grinding noise.
Keep these points in mind before you mess around with your filter:
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- Always unplug an aquarium filter before cleaning it or working on it. Always! You are working around water and electricity, and that’s a bad combination.
- Though it is probably obvious, if you are unsure please check with the manufacturer to see which components can be taken apart.
- It is very dangerous to take apart the electrical components of a filter and you should never try to do so.
Some filters are just designed in a way that makes a little sound. I loved my Penguin BIO-wheel filter on my 55-gallon tank. It made a soft gurgling sound I found relaxing, but my wife did not like it so much. I had to find another alternative, and I eventually went with an Aqua Clear filter, which I found to be very quiet (and my wife didn’t complain.)
Can You Turn an Air Pump Off at Night?
This is not nearly as much of a concern as turning off a filter. If your air pump is driving you nuts, you can get away with shutting it off at night, as long as your filter is running and doing its job.
But what if your air pump is your filter? Some of those small aquarium kits use an air pump with an air stone and a tube and call it a filter. It is supposed to work as a kind of an undergravel filter. If your “filter” meets this description, it is actually an air pump. While it may not clean the water very well, it does keep the water moving and provide an oxygenation effect.
I’ve always found air pumps noisier and more abrasive than filters. But the good news is, aside from choosing a different tank with a good filter, there are a few things you can do.
- Your first step might be to place something soft under the pump. Air pumps vibrate, and if they are placed on a hard surface they often rattle.
- You can also try putting your air pump in a lidless box (the lidless part is important, as you’ll soon see) which may help absorb some of the sounds.
- If your air stone is old consider replacing it. A gunked-up air stone makes your pump work harder.
Caution: While you may be tempted to do so, I do not recommend wrapping the air pump in a towel or similar item. Pumps produce a little bit of heat, and it’s important to let it dissipate. Otherwise, you could overheat your air pump, or worse.
What About Betta Fish?
Can you turn the filter in your betta fish tank off at night? After all, these guys can live in unfiltered setups, so what difference could it make?
Bettas do best with a filter, just like any other tropical fish. But they also have an evolutionary advantage over most tropical fish. They are anabantids, which means they can take gulps of air from the water surface as well as breathe through their gills. This helps them survive in the wild, living in nasty, stagnant puddles while they wait for the rainy season.
So, if you are a betta keeper, one of the most important questions to ask yourself is: Do you want your tank to replicate the nasty, stagnant puddles of the dry season? Or, would you rather replicate the clean, oxygen-rich habitat of the rainy season? Which do you think your betta would prefer?
We know the answer, right? So that means it is best to follow the same practices for a betta fish as you would with any other tropical fish. Keep that filter running.
Will Your Fish Die If You Turn off the Filter?
Your fish probably will not die as a result of turning off your filter for one night. If they do, you’ve got something else going on that has them in a weakened, unhealthy state.
It is also a false belief that turning off the filter for one night will kill off all of your healthy microbes and you’ll have to re-cycle the tank. Those little microbes are tough.
However, if you make it a habit to shut off your filter every night, you are putting both your fish and your microbe colonies in a bad situation. Filters not only remove waste from your tank, but they also provide important aeration. Remove the filter from the equation for a third of every day and, eventually, your tank will suffer for it.
If you have been turning off your filter each night you may have noticed other issues such as algae blooms, cloudy water, and snail outbreaks. In addition to running your filter 24/7, here are some ways you can deal with those issues:
- Cloudy Fish Tank Water Causes and Solutions
Get some help figuring out why your water has turned cloudy, and what you can do about it.
- How to Get Rid of Algae in a Fish Tank
Learn what causes excessive algae in a fish tank and how to deal with it.
- How to Control Pest Snails in a Fish Tank
Got snails? Like, everywhere? This article can help.
Turning Off the Aquarium Filter at Night
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2019 Eric Dockett
Eric Dockett (author) from USA on May 29, 2020:
Hi Stephen - Glad you like the site! You can sign up for HubPages and follow me if you like. Then you can get an email whenever I post a new article. You can also follow the topics you are interested in and you'll get an email whenever another writer posts articles on those topics.
Stephen Tang on May 28, 2020:
How do I join/subscribe into your group? I really like all your postings especially on goldfish and pet dogs.
Eric Dockett (author) from USA on September 14, 2019:
@ Richard- Are you using the correct size filter? Healthy fish should be able to escape the pull of the filter. You can try making or buying a pre-filter sponge which might help.
Richard Heinz on September 13, 2019:
I have an Aqua-Tech power filter and my fish are getting caught in the intake tube. The force of the intake is too much for the fish snd they are dying.
Eric Dockett (author) from USA on August 29, 2019:
@Catherine: You should really check the directions or contact Tetra. From just a quick online search it appears the bag goes in front, as in the water flows first through the bag and then the grid. But please check with the manufacturer if you are having issues.
Catherine on August 29, 2019:
I am a little confused hear. I have a tetra 600 crystal filter. So do i put the grid behind the crystal bag or in front. Please help.
Eric Dockett (author) from USA on April 16, 2019:
@Aldrien - That's fine. It won't hurt anything and is sometimes a necessary step in cleaning the tank. You do not want to replace filter elements that often though, as you can would reduce your bacterial colonies and cause a mini cycle.
Summernole on April 15, 2019:
Never turn your filter's off. Not with tropical fish or saltwater fish. Big mistake.
Aldrien Tan from Bukit Mertajam on April 15, 2019:
I usually turn the filter off every week for half to one hour while changing the water (usually 50% tank capacity) and cleaning up the filter. .
Would this impact the ecosystem or the balance?