How Do Fish Sleep At Night

While fish do not sleep like land mammals will, fish do sleep, even though it doesn’t seem like they ever do. Due to instinct, when it’s night time, the body naturally begins to slow down and need to rest.  Sleeping helps restore the body from the daily activities that it endures. Fish are no different and they need to sleep at night.

How do fish sleep at night? Some fish will wedge themselves into a secure spot between rocks, aquarium decorations, or aquatic plants. Some will sleep by burying themselves in the sand and gravels. Others will just float freely in place.

There are thousands of species of fish in the world and each species have their own ways of sleeping at night. The fish will usually find a place to sleep where they feel secure. Depending on the species of fish, you will notice each have their own ways and places to sleep at night. Below are a couple of species of fish that’s popular among fish keepers and how they sleep at night. Well, except for one species of fish.

How Do Betta Fish Sleep At Night?

Betta Sleeping

At night, Betta fish will spend most of their time sleeping. When they are sleeping, they will most commonly be lying on thee bottom of the aquarium tank. However, there are some Betta that prefers to sleep higher up in the tank.

For Betta that likes to sleep on the bottom of the tank, make sure to have some aquarium decorations or plants in the tank.  Bettas will sleep under or between the leaves of the plants.

For Betta that prefers to sleep up higher, you can get some aquarium decoration such as a Floating Betta Log, which you can find on Amazon. They love a great place where they can hide and sleep in.  Other Bettas will just sleep floating near the top of the water.

Betta fish is one species of fish that have the ability to sleep on their side.  This might seems odd, but it’s true.  For that reason, it inspired products such as the Betta Hammock, which you can find on Amazon.  This product adheres to the side of the tank and it provides a place where your Betta can lie on.

During the night hours, you’ll want to make sure that there are minimal lights shining into the aquarium. Low to no lights will help induce sleeping for Bettas and other fish as well.

When Bettas are sleeping, make sure to never tap on the aquarium glass. Make sure to let them sleep as waking them up abruptly isn’t great for their well-being.

How Do Goldfish Sleep At Night?

Goldfish Sleeping

At night, goldfish will usually sleep low in the water, about an inch or so off the bottom. Unlike other fish, they don’t sleep in or under any plants or aquarium decorations. Instead, goldfish will basically float or hover in the water.

With goldfish, you’ll want to keep the aquarium lights off at night. This is to help induce sleeping and help them sleep longer.  Goldfish need an average of 6-8 hrs of sleep to maintain good health.

During the day, you may find the goldfish is sleeping as well, but this is only a quick nap.  Goldfish like to take a couple of naps throughout the day.  If you see them just floating around and looking lifeless, it’s nothing to be concern about.

While they are asleep, you may notice their colors become faded.  This is normal as the blood in their body is moving slowly, which cause the faded colors.  Once they are awake, their colors will be back to normal again.

How Do Plecostomus Sleep At Night?

Pleco Sleeping

Plecostomus don’t sleep at night. These are nocturnal creatures, which means they are active at night and inactive during the day. Being nocturnal can have a lot of advantages for them, especially in their native habitat.

During the daytime hours, there won’t be too much activity coming from the plecostomus. They will most likely be sleeping. Plecostomus will find a dark place such as an aquarium decoration or plants to sleep under. For this reason, you should have a couple of plants and aquarium decorations for them.

Plecostomus will usually sleep under an object, but there are times you can find them sleeping against the aquarium glass or under a filter.  If there are no plants or aquarium decorations for them to hide under and sleep, they will usually try to bury themselves under the gravel. This is to escape the lights from the aquarium lighting and natural daylight.

At night, plecostomus will be active and searching for food in the aquarium.   During this time, you’ll want to turn off the aquarium lights as well.  This is so they’ll know it’s night time and time to come out and feed.

In addition to turning off the aquarium lights, before heading to bed, you can drop fish wafers for them to feed on.

Do Fish Swim When Sleeping?

Some species of fish actually do swim while sleeping.  Well, it kind of looks like they’re swimming, but not really.  What’s happening is that they’re just floating in the water with their fins flapping, which seems like they’re swimming.  The fish is asleep, but in order to breath, they need to move so water can pass through their gills.  As water passes through the gills, the gills take oxygen from the water and pass it through the body of the fish.

However, some species of fish don’t need to swim in order to breathe.  Fish like the Betta, Guppies, and Tetras can actually stay in one place throughout the entire night.  This is possible by using their pectoral fins to move water through their gills.  As they flap their fins, it pushes the water through their gills, which provide oxygen for the fish to breath.

How Do You Know A Fish Is Sleeping?

Since fish don’t have any eyelids, they can’t close their eyes. Without their eyes closed, fish still do fall asleep. Instead of eyelids, nature provides darkness as a replacement for eyelids.  For this reason, it’s important to turn the aquarium lights and any other lights in the house off night time.  There are a couple of ways of telling if the fish is sleeping.

Gill Movement

When the fish is sleeping, one of the things you’ll notice is their gills movement. Their gills movement will be significantly reduced. The movement of the gills is just fast enough to bring water through the gills, which provides oxygen for the fish.  In addition, their pectoral fins will flap slowly too.  This is to help push water through their gills.

Body Movement

Another thing you’ll notice is their body movement. Some fish will float or hover in the water.  It may seem like they’re lifeless, but that’s how some fish sleep.  By floating in the water, it allows water to pass through their gills, which provide the fish oxygen.  Some fish like the goldfish will hover just an inch or so off the bottom of the aquarium.  On the other hand, other fish like the Betta will float near the top of the water.

Hiding In Places

Some fish like the Tetras and Guppies will find a place to hide and sleep at night.  This is their instinct to find shelter while sleeping to avoid becoming prey.  If you have these small species of fish in the aquarium along with other fish, especially if their bigger, it’s a good idea to have a lot of plants and aquarium decorations for them to hide.

Do Fish Need Lights To Sleep At Night?

The simple answer is no. You don’t need to keep the light on at night for the fish to sleep. Keeping the lights on at night can actually cause them health problems. The reason for this is because most fish need about 6 to 8 hours of sleep each night.

In their natural habitat, naturally, there will be lights during the day and darkness during the night. In captivity, you will need to replicate what’s found in their natural habitat to maintain good health for the fish.

If you leave the lights on throughout the night, you may find that some of the fish will become ill. This is due to stress being forced on their bodies due to the impairment of the immune system. Fish need sleep to restore their immune system or other parts of their bodies.


As you can see from this article, different species of fish have their own ways of sleeping at night. Some fish will sleep in one place, some will wedge themselves between leaves of plants, and others will just sleep floating freely in the water.  For this reason, you should have a lot of aquatic plants and aquarium decorations in the tank for them to hide and sleep.  Most importantly of all, make sure all the lights in the aquarium are off at night so the fish can get a good night’s rest, just like us.

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