Discover the Surprising Truth: Do Fish Sleep? (2024)

It is well-accepted that people need a good amount of sleep to be at their best, but what about our aquatic companions? Do Fish sleep? The short answer is YES! Fishes do sleep, but every fish has a different sleeping cycle. Read along to find out!

In this post, we’re going to explore the fascinating answer to this age-old question, discuss the sleeping habits of Fish, the different types of Fish, and how to recognize when your Fish is resting.

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Introduction: Do Fish Really Sleep At Night?

Rest is an essential component of living for all living things, including Fish. So how do they obtain the proper amount of sleep? Do they really sleep at night? To answer this query, let’s explore the various kinds of Fish and the methods by which they rest.

Types of Fish & Their Sleep Patterns

Generally speaking, the sleeping habits of Fish vary slightly depending on the particular species. While some types of Fish take naps throughout the day and night, others only rest strictly at night or during the day. For instance.

  • Nocturnal Fish
  • Diurnal Fish
Nocturnal Fish
Nocturnal Fish

Nocturnal Fish:

Some species of Fish, such as Catfish, Betta Fish, and Cichlids, have an opposite sleeping schedule to most – they become lively during the night and rest during the day.

Diurnal Fish
Diurnal Fish

Diurnal Fish:

Many schooling fish, such as guppies, Corydoras catfish, and tetras, doze in the nighttime and display a more energetic side during the day.

It’s noteworthy that some fish don’t sleep at all. Sharks and some types of eel, which are predators and must remain on the alert for prey, may not sleep or take brief rests during the day.

Do Fish Sleep In Aquariums?

Do Fish Sleep In Aquariums
Fish Sleep In Aquariums

Fish do catch some sleep in aquariums, even though it may not appear that way at first glance. Fish Sleep by usually conceal themselves in the dark and become less active at night, which is a telltale indicator of their sleeping. Also, they may rest near the bottom of the tank during daylight hours, which is another indication of their slumbering.

Do Fish Sleep Upside Down?

Do Fish Sleep Upside Down
Fish Sleep Upside Down

Absolutely! Some species of Fish, such as Catfish and Cichlids, are known to take naps upside down in the water. It is worth noting, however, that in some cases, this behavior is more out of necessity than simply a need to sleep – they may be trying to conceal themselves from predators or avoid being in a light source.

Do Fish Sleep While Swimming?

Do Fish Sleep While Swimming
Fish Sleep While Swimming

Did you know that certain kinds of Fish can rest while they are in the water? This is especially common among nighttime Fish like Catfish, Cichlids, and certain types of Sharks. These kinds of Fish tend to swim slowly with their eyes shut, which is a way to tell that they are sleeping.

How to Tell if Your Fish is Asleep

It can be tricky to figure out if your Fish is catching some Z’s, but there are a few indications to watch out for. Firstly, see if your Fish is being less active, like concealing itself in the shadows or lounging at the bottom of the tank. Plus, you can note that your Fish’s gills may be partially opened, which suggests that they are asleep. Moreover, if your Fish is moving slowly or its eyes are shut, this is an additional sign that it’s dozing off.

How Long Do Fish Sleep?

How Long Do Fish Sleep
Long Do Fish Sleep

Certain types of Fish, like Catfish and Cichlids, are nocturnal and require more sleep, with some species napping for up to 12 hours daily. On the other hand, diurnal creatures like Guppies and Tetras tend to need less rest, usually getting in 6 to 8 hours of sleep.

The Sleep Stages of an Aquarium Fish

Not only do fish sleep but Aquarium fish have three distinct phases of rest. Initially, they are in a light sleep state when they are most vigorous, with their eyes open and darting around the aquarium. The second is a medium sleep stage with their eyes partially closed, and they might be found close to the base of the container. Finally, in the deep sleep stage, they become less active with their eyes shut and are likely to rest in darker areas.

How Do Fish Fall Asleep?

Fish experience slumber similarly to humans, although their strategies could differ depending on the type of species. A few fish may drift off to sleep gradually, while others could plunge into a profound sleep quickly. Additionally, some fish could possess the capability to regulate their sleep cycles, while others may not.

Which Fish Don’t Sleep?

Which Fish Don't Sleep
Fish Don’t Sleep

As already noted, some types of Fish may not have any sleep at all. Sharks, Mexican Tetra’s, a few eel species, and some Tuna, could possibly avoid sleep or have short periods of rest during the day. Also, some fish can manage their sleeping cycles, meaning they may opt to not sleep.


All in all, different Fish have different sleeping habits, so it’s essential to know when your Fish gets its shuteye. Certain species may take their beauty rest during the day, while others hit the hay as soon as the sun sets. Plus, some species do not require sleep, and others require up to 12 hours of sleep per day. Knowing how and when your fish sleep can help you ensure they get the rest they need to stay in top condition.


Some more faqs related to fish sleeping are given under;

Do fish sleep with their eyes open?

If you’ve ever been to an aquarium, you may have noticed that fish seem to be constantly staring. This may lead you to wonder if they ever close their eyes to sleep. The answer is yes – fish do sleep with their eyes open!
The truth is that fish don’t have eyelids as we do, so the only way they can “close” their eyes is by squinting them. This is a protective reflex that they use to keep foreign objects out of their eyes while they’re sleeping. That’s why it looks like they’re still awake, even though they’re not.
Another reason why fish might appear to be sleeping with their eyes open is that they are less active at night and spend more time resting near the surface of the water. This makes them more visible to predators, so they sleep with one eye open, allowing them to be more aware of their surroundings and respond quickly if needed.
So next time you visit an aquarium, look closely and you may just see a few fish napping with their eyes open!

Can fish shut their eyes?

Yes, fish can shut their eyes! Although they don’t have eyelids like humans do, fish have a nictitating membrane that works similarly to an eyelid and covers their eyes. This membrane is transparent and helps to protect the eye from damage and debris.
Most fish will use this nictitating membrane when they sleep, or when they are scared or stressed. It’s not just for protection either, some fish use the membrane to help them see better in murky water. 
Fish also have a special light-sensing organ called the pineal eye, which is located on top of their heads. This organ helps them to detect changes in light, so that they can sense when it’s dark outside and when it’s time to sleep. 
So, while fish may not be able to close their eyes like humans do, they have a few other mechanisms that help them to rest and protect their eyes.

How do fish sleep in water?

It’s a common misconception that fish don’t need to sleep since they live in water. In reality, fish do sleep, just in a different way than land animals. 
Fish don’t have eyelids like we do, so they don’t close their eyes when they sleep. Instead, they become less active and their breathing slows down. They usually take short “cat naps” throughout the day and night. 
When it comes to sleeping in water, fish have a few options. Some fish, like the clownfish and blue tangs, will find a safe spot in the coral or a crevice and wedge themselves in so that they won’t float away when they drift off to sleep. Other fish, such as the electric eel, will stay motionless near the bottom of the tank to rest. 
Some fish even sleep while swimming! This is because their swim bladders are filled with gas and act as natural life preservers. They just need to slow down their swimming speed and move their fins more slowly to get some rest. 
So there you have it: although fish don’t sleep as we do, they still get the rest they need to survive and thrive in their aquatic environment.

Do all fish possess the same sleeping habits?

Do all fish possess the same sleeping habits? No, not all fish possess the same sleeping habits. In fact, different species of fish have a variety of sleeping patterns. For instance, some fish, like sharks, can rest on the ocean floor but also stay partially alert while they rest. Other species, like guppies, will usually hide in the shadows when they sleep and remain motionless.
Some fish sleep during the day, while others sleep at night. Some species will sleep in schools, where they stay close together for safety while they rest. Other fish prefer to sleep alone or in small groups.
The amount of time a fish sleeps can also vary between species. Some fish may sleep for as little as two hours a day, while others may sleep for up to twelve hours each day.
Overall, the sleeping habits of each species of fish can be quite different from one another. It’s important to research specific species to understand their individual sleeping habits.

what time do fish sleep

The answer is that it depends on the type of fish. Generally speaking, most fish species tend to sleep during the night and are more active during the day, but there are some exceptions that sleep during the day and are more active at night
It’s also worth noting that the amount of sleep a fish gets is often determined by its environment. If a fish is in an area with lots of light and activity, it may be less likely to rest as much as it would in an area with limited light and activity. 
In general, if you’re trying to determine when a particular fish species sleeps, it’s best to do some research on that species to find out its specific sleep patterns. 
Hope this helps!

What Methodology Do Researchers Use To Determine That Fish Sleep?

Generally speaking, fish tend to sleep during periods of low activity, usually at night or in the early morning hours. This is because they’re nocturnal creatures and they’re more likely to stay in the safety of their habitat during dark hours.
In aquariums, fish will often sleep during the day when their owners turn off the lights to simulate nighttime. Wild fish will usually find a safe location near the bottom of a lake or stream, where they can hide away from predators and get some rest.
Fish also don’t sleep in the same way that humans do. Rather than getting into a deep sleep, they enter a state of rest where their brain activity is reduced, but they remain alert and can respond to potential threats.

Is it necessary for fish to have darkness at night?

Yes, it is necessary for fish to have darkness at night. Without darkness, fish cannot rest properly and will be more stressed out. As nocturnal animals, fish are active during the night and need dark hours to feel safe and secure. 
When the lights are left on in the aquarium, fish may become confused and think that the day is continuing, resulting in them not getting enough rest. This can lead to health issues such as weakened immune systems, reduced activity levels, and poor growth rates. Light also affects the behavior of some fish species. Many fish species adjust their behavior according to the amount of light available. So if the aquarium is always bathed in light, these fish may not be able to adapt and behave normally.
In addition, certain types of algae and other aquatic plants need darkness to thrive. Without darkness, these plants may die off and affect the balance of the aquarium’s ecosystem.

Why do some fish not sleep?

It may seem like fish would need to sleep like other animals, but in fact, they don’t. That’s because fish don’t need to rest their bodies like land animals do. Instead, they rely on a number of different adaptations to survive in their aquatic environment. 
Fish have an internal clock that helps them remain active or inactive depending on the time of day. This means that they stay awake during the day when there is more light and food available and rest at night. However, this does not necessarily mean that fish are sleeping. 
Fish do not have eyelids, so they cannot close their eyes to go to sleep. Instead, they enter a state of rest known as “suspended animation”, which is similar to being in a deep sleep. In this state, their metabolism slows down, their heart rate drops, and their breathing slows down. This allows them to conserve energy and rest without actually sleeping. 
Fish also have a complex set of reactions that help them stay safe while they are in this state. For example, they can detect changes in the water around them and react accordingly. This allows them to be prepared if they sense danger while they are in this resting state. 
So while it may seem strange that fish don’t need to sleep like other animals, it is actually an adaptation that helps them survive in their environment.

what position do fish sleep in

When it comes to sleep, fish are quite unique. While most animals and humans sleep in one specific position, fish can actually take up a variety of sleeping positions! It all depends on the type of fish, their environment, and the type of sleep they are taken for example, some fish like to rest near the bottom of the tank or in a crevice in the rocks. This is common for bottom-dwelling fish species like catfish or loaches. They will either lay on their sides or rest in an upright position. 
Other fish, like tetras or cichlids, will rest at the top of the tank. They usually take up an upright position, but sometimes they will curl their bodies up to conserve heat. 
Some fish, like clownfish, will rest at the bottom of the tank but will stay in an upright position. This allows them to quickly dart away from predators if needed. 
Finally, some fish, like angelfish and discus, will actually hang vertically in the water during their sleep. This is known as “vertical sleep” and is thought to help them conserve energy and oxygen. 

How do fish sleep in rivers?

First of all, fish don’t actually “sleep” in the same way humans do. They don’t go into a deep sleep and become unconscious, but rather enter into a state of rest. This state is known as “torpor” and it helps the fish conserve energy and avoid predators.
When it comes to sleeping in rivers, fishes will usually find a sheltered area away from the current and hide behind rocks or logs, or bury themselves in the sand and mud. This allows them to remain relatively still and avoid being swept away by the current.
Fish also tend to rest during the night, when there are fewer predators around, and when the current is much slower. During the day, they will often retreat to deeper parts of the river, where there is slower current and more cover from predators. Fish also adjust their sleeping patterns according to the season. During the winter months, when the water is colder and there are fewer predators around, they may sleep for longer stretches of time. In the summer months, when the water is warmer and there are more predators, they will often sleep for shorter periods of time.
So to answer your question, fish in rivers will adjust their sleeping patterns to suit the changing conditions of the river. They will find shelter away from the current and rest during the night when there are fewer predators around. They may also change their sleeping patterns according to the season.

when do molly fish sleep

When it comes to the sleeping habits of molly fish, the answer is not so clear cut. Like most other fish, mollies are diurnal creatures, meaning they are most active during the day. However, they can become nocturnal when temperatures in the aquarium become too warm. In this case, they may sleep during the day and become more active at night. 
It is important to keep in mind that mollies require a certain amount of darkness in order to rest properly. If your aquarium has bright lights that remain on for long periods of time, you may find that your mollies are not able to get enough rest. To promote healthy sleep patterns, you should make sure that your aquarium has some dark areas where the fish can retreat to during the night. 
Finally, it is important to keep in mind that molly fish are social creatures and may not be able to get enough rest if they are kept in an overcrowded tank. If you notice that your mollies seem lethargic or are not getting enough rest, it may be a good idea to reduce the number of fish in the tank or add some more hiding places for them to retreat to. 
Overall, molly fish require a certain amount of darkness in order to rest properly. You should make sure that your aquarium has some dark areas for the fish to retreat to during the night and that it is not overcrowded. This will help ensure that your mollies get enough rest.


Alex Miller

Senior Editor at

I am a passionate writer for FishyFishPet, a website dedicated to helping new fish pet owners learn about how to care for their fish and navigate the many challenges of fish ownership. On our site, you’ll find a wealth of information on topics ranging from setting up a fish tank to choosing the right fish food, as well as tips and tricks for keeping your fish healthy and happy. Whether you’re just starting out with your first fish or you’re an experienced aquarist looking for new ideas, FishyFishPet has something for everyone. Thank you for visiting our site and I hope you find the information you’re looking for.

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