How Do Goldfish Sleep – When Do They Sleep and For How Long?

Don’t we all love to click pictures of a sleeping puppy or kitten because it’s cute? But have you wondered when and how do goldfish sleep? Be it goldfish or any other aquatic fish, every animal sleeps.

And goldfish sleep with their eyes open. Lack of sleep in goldfish can cause a number of health problems. Such as bacterial infections, fungal infections, and immune disorders.

So to understand how do goldfish sleep and ensure that they get enough sleep in the tank, read what’s below.

How Do Goldfish Sleep

Goldfish sleep with their eyes open. Although they do not sleep for hours at a stretch. Goldfish will sleep in a resting phase. This means that they go through phases of activity and resting, light and deep sleep.

If you’ll notice your own goldfish, a resting goldfish might look like it’s awake but it’s actually resting or “sleeping.” In human terms, goldfish take what we think of as NAPS.

And here are some ways in which a goldfish sleeps…

1. Floating upright

If your goldfish is still for a long time, either gently drifting but steady enough to stay upright and in one place. This could mean that the goldfish is sleeping.

A sleeping goldfish may also look a bit distant and unresponsive from time to time. Slower movements, floating, and little to no response to normal stimuli. All these behavioral changes indicate that your goldfish is sleeping.

The way goldfish sleep, you might disturb them with sudden noises or tapping on the glass surface of the tank. So any unexpected sound or movement may startle them immediately.

2. Hovering at the bottom

If you have interesting toys like live pants, tunnels in the fish tank, you’ll also find your goldfish hovering slightly above the plants. The head of the goldfish hangs slightly lower than their tail when they’re napping.

3. Drifting sideways/upside down

Another common way to spot a goldfish sleeping is when they are slightly floating or drifting with their head lower than their tail. They could also be sleeping in this position sideways or upside down. Goldfish aren’t completely drifting or passive when they sleep. Just enough to keep their bodies upright and steady at the same time. And of course, with their eyes open.

When Do Goldfish Sleep

It’s not uncommon for goldfish to nap during the day. They sleep in the day and the night. However, they are used to staying more active for hunting and exploring in the day. But they sometimes do the same during the night as well.

In terms of light, goldfish sleep better at night when the lights are off or dimmed. Since goldfish can also see infrared and ultraviolet waves, they are extremely active when it’s brightly lit. Experts also say that goldfish do not see better in darkness. So sleeping during the night is more common than the day.

How Long Do Goldfish Sleep

A goldfish sleeps for as long as 8 to 12 hours every day. But they do not do this the way humans do. They sleep in small periods spread throughout the day and night. The maximum time a goldfish sleeps at a time is 15 to 30 minutes.

Most fish tanks come with a light timer that you can set for a 12-hour on/off cycle. So the goldfish will naturally get accustomed to getting more sleep during the dark and things are silent and calm.

If the fish tank is kept in a very noisy place, your goldfish will get less sleep even with the lights off in the tank.

How to Improve Goldfish Sleep

There are a few factors that affect the sleep cycle of a goldfish. Such as…

Water Temperature

The ideal water temperate for a goldfish is between 68 to 74 degrees Fahrenheit. Having said that, goldfish are quite sensitive to sudden water temperature fluctuations. Even a minor shift by 5-degrees may cause sleep disturbances in goldfish.

Do not keep the water too warm or too cold, it should be at a balanced level. This will improve their sleep significantly. And boost other factors such as metabolism, fish interaction, and playtime!

Fish Tank Size

Overcrowding can lead to stress, lack of sleep, and slow metabolism in goldfish. Does your goldfish have sufficient room in the fish tank to swim around? If not, it can cause lethargy, fights over food and space, and skin infections.

If your goldfish suddenly becomes lethargic and hardly moves, it’s a sign that may die very soon. And the number one cause for this is overcrowding.

So if you want your goldfish to sleep peacefully, make sure you limit the number of goldfish per tank. The more fish you keep in a single tank, the more distractions there will be. This means that all your goldfish are active all the time so they get little to no sleep. 


Goldfish clean their gills by making a yawn-like mouth movement. This is very common among goldfish but they shouldn’t be constantly yawning. If they do, it means the fish tank has low oxygen levels.

Toxic high levels of ammonia can also compel a goldfish to gasp for breath in water. Ammonia levels in a fish tank can increase drastically because of their food. Goldfish love to eat and this creates a lot of biowaste.

It’s important to keep the fish tank clean and ammonia-free when you have many goldfish. High ammonia and low oxygen can cause skin infections, organ damage, and other serious diseases.

Final Thoughts

Yes, goldfish sleep with their eyes open. They also sleep sideways, upside down, and tucked in plants. However, unlike other pets, they do not sleep lying down or even for a few hours at a time.

Goldfish take short snaps for 10 to 30 minutes at a time. And they sleep during the day and night. Mostly, goldfish sleep when it’s dark and calm.

After reading this article, you’ll know when your goldfish is asleep and when it’s not. Turning down the noise and reducing the brightness can help goldfish sleep better.

Lisa Thompson

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