Do Fishes Sleep in Aquariums?

Many people have pondered the question of whether or not fish sleep. And if they do, what does their sleep look like? For aquarium owners, it can be difficult to tell when their fish are sleeping since most species don’t have eyelids to close. Despite this, it’s been discovered that fish do rest and have similar patterns to human sleep. In this article, we’ll explore fish sleep patterns and provide tips to ensure a sleep-friendly aquarium environment for your aquatic pets.

Understanding Fish Sleep Patterns

While it may be hard to identify when fish are sleeping, research has found that they do go through cycles of rest and activity. These patterns are similar to human sleep but differ in certain ways.

Differences Between Fish and Human Sleep

Unlike humans, fish do not have a distinct sleep/wake cycle. Instead, they alternate between periods of rest and activity throughout the day. Additionally, fish don’t have REM (Rapid Eye Movement) sleep, which is the stage of sleep where humans tend to dream. Instead, fish have a period of reduced activity where they may remain in one spot for an extended period.

It is also important to note that the amount of sleep a fish needs varies depending on the species. For example, some species of fish only need a few hours of sleep per day, while others require up to 12 hours.

How Fish Rest and Conserve Energy

When fish rest, they tend to congregate in specific areas of the aquarium where there’s less water movement. They may also change their body position and slow their breathing to conserve energy. This is especially true for reef and coral fish who sleep in the crevices of coral reefs.

Furthermore, some species of fish have developed unique ways to rest and conserve energy. For example, certain species of fish have been observed resting on their sides or even upside down. This allows them to conserve energy by reducing the amount of effort needed to maintain their position in the water.

The Importance of Sleep for Fish

Just like humans, sleep is essential for fish to maintain their health and well-being. During periods of rest, fish are able to repair and regenerate their tissues, which helps to keep them healthy. Additionally, sleep is important for the development and maintenance of the fish’s immune system.

In fact, research has shown that sleep-deprived fish are more susceptible to disease and have a lower survival rate than fish that are well-rested.


While fish sleep patterns may be different from humans, it is clear that sleep is just as important for fish as it is for us. By understanding how fish rest and conserve energy, we can provide them with the best possible environment to help them stay healthy and thrive.

Signs of Sleeping Fish in Aquariums

While it may be difficult to determine when fish are asleep, there are signs to look for. Here are some tell-tale signs that your fish may be sleeping:

Reduced Movement and Activity

When fish are in their rest period, they may not move around as much as they usually do. Their breathing may also be slower and their fins may droop slightly.

It’s important to note that some fish are naturally more active at night, so reduced movement during the day may not necessarily mean they are sleeping. However, if you notice a significant decrease in activity level, it’s likely that your fish are catching some Z’s.

Changes in Coloration

Sleeping fish may appear paler or darker than their usual coloration. This is because they’re not moving around and their bodies aren’t getting as much oxygen as they usually do.

If you notice a change in coloration, don’t panic! It’s perfectly normal for fish to experience slight changes in color throughout the day. However, if the change in coloration is extreme or accompanied by other unusual behavior, it may be a sign of a larger issue.

Resting Positions

When sleeping, fish may take on different postures, depending on the species. Some fish will rest on the bottom of the aquarium, while others will hover in one place or rest in a sheltered spot.

It’s important to provide your fish with plenty of hiding spots and sheltered areas in their aquarium so they can rest comfortably. If your fish don’t have a place to rest, they may become stressed and more susceptible to illness.

Additionally, some species of fish are known to sleep in groups or pairs. If you notice several fish resting in the same area, they may be catching some Z’s together!


While it may be difficult to determine when your fish are sleeping, paying attention to their behavior and appearance can give you some clues. Remember to provide your fish with plenty of hiding spots and sheltered areas so they can rest comfortably. Sweet dreams, little fishies!

Factors Affecting Fish Sleep in Aquariums

There are several factors that can affect a fish’s sleep patterns in an aquarium. Understanding these factors can help create a more comfortable sleeping environment for your fish.

While fish may not have eyelids, they still require a period of rest to maintain their health and well-being. A lack of sleep can lead to stress, weakened immune systems, and even death.

Here are some additional factors to consider when it comes to promoting healthy sleep for your fish:

Aquarium Lighting and Sleep Cycles

Lighting plays an important role in a fish’s sleep cycle. In their natural habitat, fish experience a period of darkness at night, which signals to their bodies that it’s time to rest. If the aquarium lighting is too bright or on for too long, this can disrupt their sleep patterns and cause stress.

It’s important to establish a consistent lighting schedule and dim the lights in the evening to promote a restful environment. Consider using a timer to ensure that the lights turn on and off at the same time each day.

Water Temperature and Sleep Quality

The water temperature in your aquarium can also impact your fish’s sleep quality. A fish’s body temperature is closely linked to its metabolic rate. When the water temperature drops at night, a fish’s metabolism slows down, and they enter a rest period.

However, if the water temperature is too cold or too warm, this can cause discomfort and prevent fish from sleeping soundly. Make sure to research the temperature requirements for your specific fish species and adjust the water temperature accordingly.

Tank Mates and Sleep Disturbances

Some fish species may be more active at night, which can be disruptive to their tank mates. It’s important to research a species’ behavior before adding them to a community aquarium and ensure that all tank mates are compatible in terms of sleep patterns and activity levels.

Additionally, some fish may be more territorial or aggressive at night, which can lead to stress and sleep disturbances for other fish in the tank. Providing plenty of hiding places and ensuring that there is enough space for each fish can help reduce these issues.

Overall, promoting healthy sleep for your fish is an important part of maintaining a happy and thriving aquarium. By considering these factors and making adjustments as needed, you can help your fish get the rest they need to stay healthy and happy.

How to Create a Sleep-Friendly Aquarium Environment

Providing a comfortable sleeping environment for your fish is crucial to keeping them healthy and happy. Just like humans, fish need a good night’s sleep to function properly. Here are some tips to ensure a sleep-friendly aquarium:

Providing Hiding Spots and Shelter

Creating a safe and secure environment for fish to rest is essential. Adding hiding spots, plants, and caves to the aquarium gives fish a place to retreat and rest. Not only does this provide a comfortable sleeping environment, but it also adds to the overall aesthetic of the aquarium. Make sure to provide a variety of hiding spots to accommodate different species of fish.

When it comes to selecting plants for your aquarium, consider adding species that are known to promote relaxation, such as Amazon Sword or Anubias. These plants not only provide shelter but also release oxygen into the water, which helps to maintain optimal water quality.

Maintaining a Consistent Light Schedule

As mentioned earlier, a consistent lighting schedule is important for promoting a restful environment. Fish require a period of darkness to rest and recharge, just like humans. Keep the lights dimmed in the evening to mimic the natural light cycle and ensure that the aquarium isn’t overexposed to light during the day.

It’s also important to consider the type of lighting you are using. LED lights are a popular choice for aquariums because they are energy-efficient and can be programmed to simulate natural light cycles. Some LED lights even have a moonlight setting, which provides a gentle glow that can help fish feel more secure at night.

Ensuring Optimal Water Quality

Fish sleep better in clean and healthy water. It’s essential to maintain optimal water quality by performing regular water changes, testing the water parameters, and ensuring that the aquarium is properly filtered. Poor water quality can lead to stress and illness, which can disrupt a fish’s sleep cycle.

When performing water changes, make sure to only change a portion of the water at a time. Drastic changes in water chemistry can be stressful for fish and disrupt their sleep patterns. Testing the water regularly can help you identify any issues before they become a problem.

Finally, make sure to select a filter that is appropriate for the size of your aquarium and the species of fish you are keeping. A filter that is too small or too weak can lead to poor water quality, while a filter that is too strong can create a current that disrupts fish sleep.

By following these tips, you can create a sleep-friendly aquarium environment that promotes the health and happiness of your fish.


So, do fishes sleep in aquariums? Yes, they do! Although it may be more challenging to identify when your fish are sleeping, it’s important to provide them with a sleep-friendly environment. By following the tips in this article, you can ensure that your aquatic pets are getting the rest they need to stay healthy and happy.