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Not Killing Your Fish Guide | Can I Turn My Filter Off At Night?

Was your filter designed by this guy?

Was your filter designed by this guy?

You know what's useless? Common knowledge. The sort of knowledge that makes claims, but never supports them. Aquarium filters can be loud, even if you buy a good one, and some people just want to be able to turn the filter off at night.

Now the common response to the 'My filter is too loud and my boyfriend is going to murder all the fish if they keep him awake for one more night,' dilemma is to say 'Get him some ear plugs,' or 'Buy a better filter'. Both of those options are viable, and if your filter is unsuited for your tank, then sure, you might be better off buying a new filter.

Then again, you might like your filter. You might have spent good money on it. You might not want to buy an endless stream of filters hoping that one will be quiet enough not to disturb your night's sleep. In this case, your desire to turn the filter off at night may very well overwhelm your desire to keep your fish 100% healthy.

The problem with turning off the filter isn't that the ammonia and wastes will build up to toxic levels overnight, it is rather that (according to some) if you turn your filter off overnight you will kill the bacteria in your filter. Your tank will cycle all over again, ammonia will build up and your fish will die. DIE! (The bacteria in the filter are responsible for converting ammonia into less toxic compounds, but let's face it, if they threaten to die after an 8 hour fast, I don't know how responsible they can really be considered to be.)

In my experience, bacteria are normally more robust than to die if they are not fed for 8 hours. This is assuming you are using an internal filter or a filter that remains saturated in the tank water all night, so they don't dry out and become inert.

In the case of filters which stay wet, bacteria will still be floating in a tank full of ammonia, its just that water won't be drawn past them. Thus, I posit that it should be a okay to turn the filter off overnight. However, unlike other online sources (I'm looking at you, Yahoo Answers,) who simply make statements without evidence, I plan to show my working on this front. It may be that I am wrong, in which case we will all know for sure that you must run your filter all night.

I will be cycling my tank, turning it off from 11pm to 8am, and then leaving the filter to run for the rest of the day. To make things a little more difficult, I am going to be starting a cycle from scratch, meaning my bacteria will not have built up at all when this experiment begins. We'll know if the bacteria die every night, because my tank will never cycle properly if this is the case.

Water will be tested at 8am , before the filter is turned on, and at 10.59 pm, before the filter goes off. If, as people claim, ammonia convering bacteria, (reputed to be Ammonia will simply build up to toxic levels, and because I keep interrupting and killing my bacteria every evening, it will not come down to 0, as it should.

Stay tuned, this experiment will run for an entire month.

(Oh, and fear not, this is a fishless cycle, so no innocent fishies will be harmed in this experiment.)


Betta Matt on September 10, 2019:

Hello I'm sorry for the late reply, but glad to be able to help if I can.

Most of the time white specks can be from a recent water change and they can float around until the filter circulates them. Usually you can disturb the gravel when doing a water change and you can see many particles float around. Also, this can be caused if you have certain type of Algae called String Algae, it's basically harmless unless it builds up alot, but if you do frequent water changes. (atleast 10% of your tank per week and 25-30% monthly it should be fine. Every 3 to 4 weeks change filter for a healthy good bacteria tank.)

But when doing water changes this can cause blooming from an excess buildup of carbon that your filter has used up and passed on or; a whitish, milky colored water as new bacteria sets up in the tank, which usually clears up in a few days. (Another thought is calcium tablets, if so reduce those even if you have Invertebrate types like snails.)

I always recommend using a gravel pump every 3-4 weeks on an 25-35% water change while changing filter. It really helps out water quality.

After changing most of the water and issues still persist this could be due to alot of build up and a whole tank clean might be required, but usually after using a gravel vaccum this should help mostly. (do not recommend a whole tank change; as in removing everything and starting over as this would be a last resort and can be stressful for the fish) You can also buy sponges at your local pet store (make sure they are from pet store) And go over your entire tank with them but make sure to leave some algae for your other tank friends, snails if you have them. Use an unopened cheap toothbrush under tapwater to clean your tank trimmings too, like rock formations, pirate ships, bubblers, this will also help with water quality, and leave the gravel alone to gravel vaccums which you can pick up at your pet store.

Just make sure you do weekly 10% water changes, and 30% monthly. You should do 10% weekly and 50% water changes monthly on under 20 gallons to insure tank stays maintained. A clean tank is a healthy tank!

Also those with loud filters I've noticed if you set a gallon jug of conditioned water for your tank on the side and add it to the top when it goes low this should help alot with filter noise. Just make sure the water level is the same point where the water is flowing out from your filter/pump.

I hope I can help with anyone having any problems with their Aquarium setup. I've had mine for quite sometime and I know the frustration you can get trying to help out your fishies in the tank and trying to figure out whats going on!

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Scotty1979 on May 15, 2019:

I seen quite a lot off white speaks in my aquarium.

I went and done a 70% water change today and they are still there

I have a 110 letre tank with 4 fish in it

Betta Matt on May 01, 2019:

I wouldn't recommend turning off your Aquarium pump and filter. It cycles the water to help oxygenate the fish and the carbon in the filter keeps your water cleaner and helps to manage dangerous pH spikes along with your water conditioner. About the bacteria; There's bacteria in your aquarium gravel, so if you do turn off your filter I would not recommend doing so for more than a couple of hours to keep that good bacteria up and the aquatic life healthy. I mean we do get power outages sometimes do to the weather, ect so it should be fine no more than 2-4 hours as the bacteria will come back rather quickly, just watch out for aquarium bloom (cloudy water.)

Tank filters can get pretty loud. Usually you can make them more quiet by regularly changing your filter every 3-4 weeks. When a filter is past due the water will rise in the pump and can gurgle, bubble and sound mechanical. Also keep your tank full, when water evaporates the water cycling into your tank needs farther to go thus making even more trickling sounds atop the water.

I usually buy gallons of water at the local grocery (wouldn't recommend using the store bought water though lol. I've only used conditioned tap water.) When you're done using the store bought water, just fill up the gallon jugs with tap water and use your water conditioner for a gallon and let it sit and get room temperature. You then have conditioned water at hand when you need it. I'm not sure you could eliminate all the noise but should be able to get it much quieter for when you need to sleep.

Steve sheppard on December 17, 2018:

I didn't intentionally turn off my filter. After a few minutes of tank maintenance I had not plugged the filter back in correctly. Therefore, for at least 12 hours there was no water being passed through the filter media. The next day I realised my mistake but today, a day after the incident there is signs of problems with my fish, heavy breathing and stress, after 15 years in the hobby I know when something isn't right.

A 40% water change and extra water agitation added to hopefully increase O2 levels and they were back to normal. The only thing that could have caused this was the filter black out and I suspect the bacteria dieing off is causing the tank to either partially cycle or maybe even cycle all over again. Personally, I think the main issue is the drop in oxygen being provided to the bacteria, considering they are aerobic and need 02 to actually respire (live), where as food (ammonia/nitrites) is mainly neccessary for energy to reproduce.

Fishsave on November 29, 2018:

Seriously first world problems. Listen to y’all “ I bought fish I’m responsible for but can’t sleep so let’s risk the fishes health since we’re all princesses” find a new owner for your tank that appreciates them or get a new filter ya lazy people

William on September 30, 2018:

I'm so used to hearing my filter all night that i can sleep with it beining so loud.

Naomi Gordon on August 14, 2017:

Do not turn your filter off overnight!!!!! I did... and within 3 nights of doing so... the third night I woke in the middle of the night to find all 3 of My fish were dead!!

Natalie blackwood on April 01, 2017:

I have three tanks at home one community tank guppie mollies tetras my other tank in convicts sharks and barbs i have bubble blower lenght of my big tank and have turned off the internal filter over night still was fine left the heater and bubble blower on tho and they xid fine not sure of i wanted to do it over night every night tho

... on September 14, 2016:

What are reasult

Mat on July 25, 2015:

In larger tanks you can turn off the filter as long as you have plenty of air flowing through the aquarium. The little treasure chest that bubbles open isn't sufficient. I run my 120gl two filters from 5:30 am till 10:30 pm with 2 single tube aerators on large porous stones and one double tube on a pipe with holes drilled running the length of the tank under the rear rocks running constantly 24/7. Have been doing so for a year and 3 months now and have only lost one fish during a 9 hour power outage.

Isabelle on August 02, 2014:

I also can't sleep at all! But I don't want to kill them! I feel like there is a waterfall in my room!

ckb on May 08, 2013:

I have tested this theory ..and it is safe. I did it to replicate the environment which fish thrive in, drying the dry season there is less running rapids than given in wet season (seasonal), however it will de oxygenate your water. I wouldn't recommend doing this unless you have a "plus "plus size" tank 55 or bigger .

isabella on June 17, 2012:

I actually find the sound of trickling water relaxing

Acelaser on May 22, 2011:

There are tons of ways to work with filters to make to sound less noticeable. The easiest and cheapest is to put a fan, air Puifier or white noise machine between you and the aquarium. Also make sure the water levels in your filter are correct, this will lessen gurgling, bubbling and dripping sounds. Sponges made for aquariums placed strategically in your filter can really help too...

lady on January 05, 2011:

I have a whisper brand and it is not loud but the air pump is making loud bubbles heeelp

Becky on October 18, 2010:

my filter is submerged to about 1/2 an inch and has an arm that has to hang above the water so its the sound of the water running into the tank that keeps me awake rather then the actual filer, it sounds like im sleeping next to niagra falls!! please tell us if we can turn it off at night?? x

Anonymous on October 09, 2010:

ear plugs give me head aches and i don't want to kill my beautiful fish, but i just cant sleep at night, my filter is to expensive to replace and i want to know if i can turn it off at night, pleeeeaaase tell me the results!!! im ready to take a hammer to my fish tank sometimes, it is just sooo loud!!

tkimoro on September 06, 2010:

...uhhh- what happened? Did it work or not?

Jamie on July 31, 2010:

@ falalaharaha I second that!!

falalaharaha on June 03, 2010:

please do answer this! my fish's filter gives me insomnia :[

newbowl on May 04, 2010:

I wondered if you ever got a chance to finish this experiment? I have just found this page after reading countless baseless "answers" and I appreciate that you actually want to test it.

Hope Alexander (author) on September 01, 2009:

Unfortunately, I've had a break in this in that the fish tank had to be emptied and moved. This experiment will have to wait for a little bit. Extra information from experts suggests that the bacteria definitely won't die en masse overnight, but deoxygenation may occur and water quality may very well suffer.

I may have to run this in a separate, smaller tank with a more average filter. I have a power filter on the main tank at the moment and it well over filters the water, so it may not be replicating the results most people would see.

Tomgeekery on September 01, 2009:

I know it's not a month yet, but how's the experiment going?

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