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Do Goldfish Sleep? Here’s How to Tell by These 3 Strange Habits

Lindsey Stanton Profile Picture

By Lindsey Stanton


They do indeed!

Most animals need some time to “recharge their batteries,” and goldfish are no exception.

FACT: Goldfish actually sleep with their eyes open because they don’t have eyelids!

This means suddenly turning on the lights can be quite a shock for them.

How do you know when your fish is catching some zzzs?

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Exactly How do Goldfish Sleep?

  1. Once it gets dark (and sometimes in the late evening), you may see your fish “hanging” in midwater, dorsal fin slightly relaxed, fins outspread gracefully.
  2. Every so often, they might move their fins to keep their balance.
  3. Their colors might even fade a bit…but quickly return once they wake up.


Just how deeply do they sleep?

While we don’t know exactly, it would seem pretty lightly due to two facts:

  1. Unlike sleeping people, their brainwaves don’t change1. Mammals have EEG waves that characterize that they are asleep.
  2. REM sleep, another sign of a very deep sleep, just doesn’t happen with cold-blooded animals such as fish.

They do have reduced activity, and their metabolism slows, so there is definitely

It’s really important not to keep the goldfish’s light on in the aquarium 24/7. The natural day and night cycles are essential for their health and have been proven to affect their immune system.

Sleep probably also serves other purposes for fish as well, some of which may not have yet been discovered. We know it serves to help restore their energy.

Get this:

In the wild, goldfish even have what seems to be a “yearly sleep” of hibernation when they don’t move around or eat much.

They spend the cold winter months near the bottom of the pond, totally oblivious to everything and seem to be living in slow-motion.

goldfish with gravel
Image credit: Lawrencekhoo, Wikimedia Commons CC4.0


Considering how important this period of nightly rest is, it’s a good idea not to do anything that might startle your fish unexpectedly and cause stress.


What About Other “Sleeping Positions?”

Sitting on the bottom of the aquarium isn’t a sign your fish is asleep, especially if that is happening during the day.

Actually, looking droopy at the bottom of the tank probably means your fish isn’t feeling well due to a problem in the aquarium or with the fish.

Bottom sitting could be an indication of issues with the water quality, infection, illness, or even constipation. Constipated goldfish may have trouble sinking to the bottom of the tank.

Does it look like your fish is sleeping upside down or on its side?

If so, chances are it might have swim bladder disorder or another health issue and is definitely not dozing.

A belly-up fish (if it is still alive) is not in a natural sleeping position at all and is probably feeling stressed because it isn’t normal.

Credit: M-Production, Shutterstock

Swim bladder disorder can cause the fish to completely flip upside down and cause a lot of difficulty when swimming. This is due to the swim bladder organ being filled with air and unable to regulate itself properly.

You can click here to read more about Swim Bladder Disorder.

A fish laying on its side is usually having serious problems as well and may be affected by an internal bacterial infection or caustic burns from high ammonia or nitrite levels.

The fish will usually be very lethargic, but that is because it is feeling bad rather than sleeping.

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Goldfish Sleep FAQ

Q. How long do goldfish sleep?

It’s hard to know exactly, as some goldfish seem to enjoy taking a late afternoon siesta while others remain active all day until nightfall.

Most likely, their sleeping habits follow the day and night light cycle.

Q. Is your fish sleepy if it yawns?

Probably not.

Yawning is actually your fish clearing its gills by flushing water over them backward, not necessarily a sign that it is feeling tired.

Q. Where do goldfish sleep?

Goldfish can sleep anywhere in the tank, but usually, they stay in the mid to lower region of the aquarium. They will usually be suspended in the water no matter where they are.

Q. Are goldfish nocturnal?

While animals that are nocturnal sleep during the day and are awake at night, goldfish don’t fall into that category.

Not all fish sleep. Fish like Tuna have to swim in order to respire.

Q. What about blind or visually impaired fish?

Though species of goldfish such as the Black Moor do not see as much as other varieties, they can still sense light and don’t rely completely on their vision to tell them when it is time to “go to bed.”

If you're new to the world of goldfish or are an experienced goldfish keeper that loves to learn more, we recommend you check out our best-selling book, The Truth About Goldfish, on Amazon.

From diagnosing illnesses and providing correct treatments to ensuring your goldies are happy with their setup and your maintenance, this book brings our blog to life in color and will help you to be the best goldfishkeeper you can be. 

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Wrapping it All Up

Now I’m turning it over to you…

Have you ever caught your fish in the middle of its sleep?

Do you think your goldfish has dreams in the wee hours of the night?

I want to hear your thoughts in the comments section below.



Featured Image Credit: Jan Smith, Flickr

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