Do Swordtails Need Light At Night?

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Swordtails are fascinating species of tropical fish that make a great addition to your tank. Many aquarists are fond of swordtails because they are unique, hardy, and easy to care for. One of the most asked questions by swordtail-keepers, however, is if swordtails need light at night.

Many people are confused about whether or not swordtails need light at night. While they require proper lighting during the day to stay active and healthy, it is important to keep them under minimum or zero lightings for a few hours each evening. Like all organisms, swordtails need rest too. Therefore, keeping the lights off at night will favor your swordtail’s rest or sleep routine.

This article will help you understand how and when to provide your fish with light so that they can enjoy their rest time in peace.

Do Swordtails Need Light?

Have you ever heard of the circadian rhythm? It means “daily rhythm.” So the circadian rhythm is a 24-hour cycle that influences various functions in living beings.

It is also known as “daily rhythm” and helps us figure out when to sleep and when to wake up with the help of light.

The trick is finding that balance between bringing them out into daylight for optimal health and giving them the opportunity for rest or sleep by turning off the lights at night.

Providing lights for a maximum of 8-10 hours a day can be more than enough for your swordtail fish. However, too much exposure to light can be dangerous and even cause death in some cases.

To make sure your swordtail is getting the right amount of light, you should invest in a timer that will turn off lights after they’ve been on for several hours.

You can also use a “moonlight” or low-intensity night light if it’s dark enough outside at night and you want something comforting to look at while you’re sleeping.

Do Swordtails Need Light At Night?

Swordtails require optimum lighting during the day to stay healthy, but they also need rest. That’s why you should turn off the lights at night and let them get some sleep for a few hours after playtime in daylight or around artificial light during the daytime.

They do require some level of lighting to stay healthy, but they also need rest during the “night time,” so they need to balance daytime playtime (under lights) and nighttime sleep times without artificial light sources.

Too much light can deteriorate the health of your fish, as they won’t be able to rest or sleep with the lights on. Therefore, it is better to leave the lights off at night.

Similarly, leaving the lights on for too long will cause rapid algae growth, which is also not beneficial for your swordtail. Hence, you should turn the tank lights off at night because swordtails do not need light.

How Much Light Do Swordtails Need?

Without enough light, your swordtail will become stressed. It’s important to have the right amount of light at different times throughout the day and night.

It’s best to provide swordtails with a well-lit aquarium during the day. Swordtails need as much light on their tank as possible when they’re awake and active for them to thrive. This will help keep your fish happy and healthy, too! You should also give them at least five hours of darkness each night so that they can sleep.

Some swordtails will need a moonlight glow during the night to help them see better. However, it would help if you only used it at night when your other lights are off, and they’re resting in their tank. This way, you’ll be giving them some light without disrupting their natural cycle of restful daytime sleeping and active nighttime hunting.

You should also make sure that your swordtail tank is set up, so they get a lot of light during the day. A well-lit aquarium will not only keep them happy and healthy, but it’ll help you spot any problems with their health or behavior more easily.

What Type Of Light Is Best For Swordtails?

The type of light you need to provide for your swordtail will depend on the time of day and night.

The best lighting for aquatic species is full-spectrum fluorescent bulbs that provide a natural look in your tank and allow plants to grow as well. Some people prefer artificial plant lights, while others use natural sunlight from a window.

A swordtail will not be happy without enough natural daylight throughout its tank and a well-lit aquarium during the day. This is important for their health and well-being!

What Happens If You Have Tank Lights On At Night?

If you have the tank lights on at night, this may disrupt their natural cycle of sleeping and waking. In addition to that, some fish are more active during daylight hours while other species prefer darkness- so it’s important to consider your pet’s preferences before deciding what time they should turn off the aquarium light.

It would help if you also thought about the fish’s mood. For example, Swordtails are generally active during daylight hours- so having lights on at night may annoy them as they do not get a chance to rest.

On the other hand, some fish species prefer darkness, and you must consider these preferences when deciding what time they should turn off the aquarium light.

How Can Night Lights Affect My Swordtail?

Swordtails are nocturnal fish that we can find living in freshwater habitats. However, they have been said to live about 70% of their time during the night, so it is not uncommon for them to spend some time each day with lights on.

That being said, if they do not need light at night, then why would you want one for them?

A night light is an unnecessary expense for a nocturnal fish. They only need to see at night when looking for food, so it would be in your best interest to have any lights you may want on during the day and off at night.

A strong light source such as a fluorescent bulb can cause harm to the eyes and disrupt their natural sleep cycle.

Light can be detrimental to your nighttime fish since it can disturb them by disrupting the important biorhythms in place for a nocturnal animal. Therefore, night lights are not required, but they may help keep an eye on any sudden movement or other changes in behavior during the dark hours of the night.

If your swordtail does not require a light at night, there is no reason to use one.


Here are some of the most frequently asked questions regarding swordtail’s nighttime routine.

Do Swordtails Sleep At Night?

Yes, swordtails sleep, but they have different sleeping behavior. It is different than mammals. The sleep patterns of fish vary widely with other animals. However, all organisms need sleep.

Swordtails do not have eyelids, which means they cannot shut their eyes while sleeping as we do. We can identify the sleeping behavior of swordtails by a slower heartbeat and a low rate of movement.

Can Swordtail Fish See In The Dark?

Swordtail fish can see in the dark by using an organ called a “pineal eye.” This is how they take care of their business during the night. They have a small pineal gland on the top of their head that converts light into chemical signals to help them see.

So they can see in the dark, even though it’s not clear as in the day, which helps swordtails hide from predators and find food. In addition, your swordtails will not bump into the tank glass.


Swordtails are nocturnal fish, so they don’t need light at night. However, if you choose to use tank lights, try not to leave them overnight because it can affect your swordtail’s circadian rhythms and make the fish more vulnerable to stressors such as disease.

Make sure to keep give them lights for only 8-10 hours a day and switch them off at night so they can rest for a beautiful day tomorrow.

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