Do Swordtail Fish Sleep?


Do Swordtail Fish Sleep?

Our bodies need sleep for well-being and optimal health. Apart from rejuvenating and restoring the body, sleep solidifies and consolidates information. Determining when a person is asleep is easy.

However, when it comes to swordtail fish, the case is different. Dictionaries define sleep as a situation where the animal closes the eyes and shuts down part of the brain – neocortex.

So, it can be hard to provide an answer to the question:

So do swordtail fish sleep? Yes, swordtails do sleep, but they have a very different sleeping behavior compared to humans or mammals.

Swordtails have no eyelids or a neocortex. To answer the question, I had to look at their behavior in addition to their anatomy. Just because fish are different from the land mammals, it does not mean that they do not require sleep or rest.

Swordtails sleep, but their sleep is very different from that of humans and other animals. A study that the University of Zurich conducted, involving 200 animal species including fish, showed that even though the sleep pattern of fish varies widely, every animal sleeps but in its unique way. Most animals require some time to rest and to slow down the functions of their bodies.

And even though swordtails might not fight perfectly in the definition of sleep the dictionary provides, they have a time of slowing down and inactivity, which forms their version of sleep. What is involved in the version of swordtails is a slower heartbeat, low rate of movement.

The two signs should tell you that the metabolic rate of the swordtails has reduced to conserve energy. In the study that I have just mentioned, the researchers relied on several factors to describe sleep. The factors include:

  • The sleeping posture of a species such as lying down for human beings or caving while sleeping for some species of fish
  • The behavioral quiescence maintenance such as slowing down or inactivity
  • It becomes hard to arouse them
  • The state of sleep is reversible. In other words, someone can easily awaken them

Using the definition, it is right to say that swordtail sleep each day.

Swordtail Fish Sleeping Behavior

If you have swordtails in your aquarium, you already know that they are always swimming except when stressed, sick or resting. Just as you expect with the other animals, swordtails will get tired after their swimming throughout the day and they will stop moving completely or sleep to take rest.

Sleeping provides the body with a good chance to restore energy and to relax naturally. The mobile nature of swordtails consumes a lot of energy, particularly when swimming, and as a result, they need sleep to rebuild the energy they require to keep moving. If a swordtail fails to sleep properly, its body will get disturbed, more like that of a human being.

The primary reason for sleeping is to restore body energy or to rest, but swordtails also sleep for other purposes. They use their eyes to do several functions such as hiding, searching for food and to swim around the aquarium tank.

That is because water waves disrupt their sense of smell making the eyes the only reliable means. In other words, the swordtail has to rely more on its eyes to survive inside the water. That is why they need some time to rest their eyes and sleep. With enough sleep, the swordtails are able to continue swimming.

The sleeping cycle of swordtail fish – I am speaking about those you keep in your aquarium tank – depends on the interior lighting. The fish stay awake during the day and then rest at night. Inside the aquarium tank, light is the determining factor of day and night for your swordtails.

If the surrounding environment is dark, your swordtails will start showing sleeping behavior. So, if you left your fish in darkness for a few minutes, you are likely to find them in sleep. By living the light on both day and night, you will find the swordtails taking rest in intervals but they will not rest calmly.

You have to set the aquarium tank environment as dark for some time to allow the swordtails to relax and sleep. Failure to do that, you will stress the fish because of inadequate quality sleep.

Swordtails like sleeping in the dark but unlike human beings, they do not have eyelids. In other words, they cannot close their eyes. So, when checking whether your fish is asleep you should never look for that. Here are some of the signs to observe.

  • Inactivity for extended periods
  • The fish moves to the surface or bottom of the aquarium tank
  • Slowed breathing gills
  • Slower response to the external stimuli
  • Regular sleeping patterns such as time and way of sleeping

You can use the tips to understand the sleeping routine of your swordtails. When sleeping, their bodies are usually idle but you will always see flicks of the fin because that enables them to remain stable in water.

Most people claim that their swordtails drop down to the base of the tank or hide in the plants to sleep. So, if you find your fish hiding under a leaf and it is inactive, most likely, it is asleep.

Do not disturb the fish because any disturbance can stress them. If you turn off the lights, you are likely to notice that the swordtail will float at the surface, particularly those that are pregnant. The behavior is uncommon during the daytime – or when the lights are on.

So, if you find the swordtail floating in the tank and the lights are on, you should know that something is wrong. Consult an expert for the best solution.

Swordtail Fish Sleep Requirements

It is clear that swordtails sleep and they need sleep for a healthier life. However, because their sleeping habit is very different from that of human beings, you will have to be more attentive to know whether they are sleeping or they are just stressed or sick.

If you are a swordtails owner, you will have to ensure that you are taking care of all their sleeping essentials and that the room is dark when they are resting. To conserve more energy, which they require to swim around throughout the day, you will have to make the room dark regularly. Ensure that the water conditions are right and add more live plants in the aquarium.

Setup Aquarium Lights on a Timer

The lighting timer setup is among the easiest tasks. Even though the process varies from one model to the other, you will never have problems completing the task. Start by purchasing a reliable aquarium light timer and connect it to a power outlet.

After that, connect it to your aquarium light so that you can start the programming part. Depending on when you want your swordtails to sleep, you will be able to set when you want the lights to start functioning and when to go off. After setting up the lights properly, you should expect everything to function properly.

Related Questions

Can swordtails see in the dark?

Swordtails tend to sleep at night. Even though they do not close their eyes, they rarely move a lot. After turning the lights on, they will take some time to get back to their normal state. The fish can sense the happenings around them. And because they do not receive more light as humans receive during the day, they can see in the darkness, but not in the best way.

Do swordtail fish sleep upside down?

It would seem unnatural if you woke up one morning and found your swordtail sleeping upside down at the bottom or top of your aquarium tank without moving. This is always a bad sign and most likely your swordtail fish is dying.

In most of the cases the unnatural swimming of fish is caused by swim bladder disorder. This is the organ which controls the swimming of the fish. The swim bladder can malfunction due to some disease or bad water parameters.

Usually this problem is fatal, so you can’t really save the fish.

I’ve seen a video on Youtube, where a doctor saved a goldfish from this disease with a surgery, however in case of a swordtail I don’t think it would worth the effort.

Can swordtails sleep when lights are on?

Swordtails require at least 12 hours of light during the day to remain active. Without light, the fish will lose their color and might stop eating, become ill or lethargic. However, if left on 24/7, the aquarium lights will disturb the sleeping of your swordtails.

Lack of good sleep will generate more stress, which can kill the fish. Give the swordtails a good time to enjoy their sleep. Remember to turn off the lights at night or use a timer.

Do swordtails need light at night?

Swordtails do not need any ambient light. It can be complete darkness at night and they will sleep just fine. If you keep your swordtail aquarium in your room, where you have a delicate ambient light, your fish will still sleep well.

So whether it is pitch-black or there is a source of light, swordtails will be able to rest, just like humans.

Swordtail Fish   Updated: October 7, 2019
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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