Can Fish Sleep With The Filter On? What You Need to Know

So, you're wondering if your fish can sleep with the filter on at night? In this article, we will discuss if it's necessary to turn off the filter during nighttime for your fish to get some rest.
Can Fish Sleep With The Filter On

Can fish sleep with the filter on is a question many fish tank owners have asked on forums all over the internet. 

It’s an easy question to answer for you, so let’s get to it.

Can Fish Sleep With the Filter On?

Every fish is different, but most fish can sleep with the filter on without any issues.

I advise you not to turn your aquarium filter off at night, and to leave it running 24/7 for the following reasons.

Water Quality

Turning the filter on and off may cause fluctuations in water quality. The filter removes debris, uneaten food, and other waste from the water.

The filter also houses beneficial bacteria that convert harmful ammonia and nitrites into less toxic nitrates, thus keeping the water clean.

By turning off your filter, you risk increasing ammonia levels and crashing your nitrogen cycle.

Oxygen Supply 

Aquarium Gas Exchange

Fish and beneficial bacteria need oxygen, and the filter helps maintain necessary oxygen levels. 

The filter’s outlet creates surface agitation which allows carbon dioxide to leave the water, and fresh oxygen to enter.

Without the filter running, oxygen levels could drop, leading to your fish experiencing stress or even suffocating.

Fish lying on the bottom of the tank, or gulping in the air at the water’s surface, could be a sign of having low oxygen levels.

Stress Reduction

Dirty water and/or low oxygen levels will cause your fish to become stressed.

Stressed fish have a lower immune system which could lead to them getting infections and illnesses such as:

Clean water = happy fish!

Why You May Want To Turn Off The Filter At Night

Why You May Want To Turn Off The Filter At Night

There are 2 main reasons fish keepers may choose to switch their filters off at night.

1. Reducing Water Current

Many keepers worry that their fish is getting blown around the tank by the water current.

If that’s you, there are a few things you can try.

Reposition The Filters Output Nozzle

Turning it towards the side or a corner of your tank will reduce the water flow throughout the rest of the aquarium.

Turn Down The Filter’s Flow Rate

If your filter has an adjustable flow rate, turn it down and see how your fish gets on, this is especially important for long-finned fish such as bettas.

If you can’t adjust the flow rate on your filter and you are looking to upgrade, you can’t go wrong with the Fluval 07 range.

Rearrange The Tank Decor

If the above don’t work you could rearrange your tank decor to deflect the water flow away from the part of the tank where your fish sleeps.

Provide Hideout Shelters

There are plenty of options for providing your fish with some shelter.

Hideout caves come in a wide variety of designs, you’re sure to find something that fits the design of your aquarium.

Aquarium Hideout Cave
ZooMed Ceramic Betta Log
Shipwreck Aquarium Ornament

Something as simple as a clean terracotta plant pot laid on its side is ideal.

2. Noise Reduction

Some filters can produce unwanted noise when running.

HOB filters have that darn waterfall noise, while some canister filters can hum, buzz, and vibrate.

If you want to avoid the filter noise stopping your fish (and you!) from catching some zzzzz’s, I have shared my successful strategies for reducing filter noise in my how long can you leave a fish tank filter off article.

Air Pump And Filter On A Timer

A middle ground between keeping the filter on and turning it off is using an air pump at night to maintain oxygen levels in the tank.

Air pumps create less current than HOB or canister filters, making the environment more favorable for fish that require calmer water for sleeping.

You can use a programmable timer to have the filter run intermittently, ensuring water is getting some form of filtration.

AquaMiracle Lithium Battery Powered Portable Aquarium Air Pump
BN-LINK BND-60/U47 Indoor Mini 24-Hour Mechanical Outlet Timer

Closing Thoughts On Can Fish Sleep With The Filter On

It’s perfectly fine for fish to sleep with the filter on at night.

You really should prioritize your finned friends’ needs and keep the fish tank filter running 24/7.

It maintains oxygen levels, keeps the water clean, and ensures a stable and stress-free healthy environment for your fish.

Adding a few hideouts will make sure your fish has somewhere it can feel safe and get some quality sleep.

Check out the aquarium health section for guides and tips to keep your aquarium in tip-top shape.



Hey, fellow fish enthusiast 👋! I'm Paul and I've been an aquarium addict since I won my first goldfish at the fair many years ago. Let me share with you the knowledge that I've gained along the way (and avoid the mistakes I've made!), so you too can create an underwater paradise for your aquatic friends.