Do Fish Need Darkness to Sleep? Do They Need Light at Night?

No matter where you live, darkness is a necessity for sleep. So it follows that for fish, this natural requirement applies as well.

The question of whether or not we should give fish darkness to sleep was first raised by a recent study that showed that Zebrafish deprived of darkness exhibits physical and behavioral changes such as slower growth and increased aggression.

How long do fish sleep?

Fish sleep for two phases, one during the day and one at night. The time that they are asleep during the day depends on the species of fish.

Factors that determine how long they sleep during the day include whether or not they are seasonal spawners, whether they are migratory, if they are diurnal or nocturnal, the water temperature, the amount of light in their environment, etc.

Do fish sleep at night?

No, they do not. It is believed that they may experience some form of sleep-like state in their off-hours, but they are generally awake throughout their lives.

Do fish sleep during the day?

Yes. Some species will experience a sleep-like state during the day. The most common sleep-like state in fish is known as the “nap” and is normally associated with the timing of migrating fish.

Why are my fish more active when the light is off?

As these fish are not actually sleeping, they are more active because they are more alert and awake. In the dark, they are able to sense their environment better, detect predators and prey faster and more efficiently, and are able to move and maneuver better.

Do aquarium fish need light at night?

Light at night is beneficial for some fish. Some fish need specific wavelengths of light for them to function, and for others, there is conflicting evidence about the need for light at night.

Do fish need blue light at night?

The presence of blue light at night may inhibit the release of melatonin in the pineal gland, which is necessary for the suppression of reproduction in female fish.

Do fish need UV light at night?

UV light at night can be beneficial for some fish, but it can also be harmful. UV light at night may help fish with skin conditions like redness or inflammation.

Are there any fish that don’t need light at night?

Some fish can live just fine without light at night, while others prefer it. The need for light at night varies among fish species.

Can fish see in the dark?

No. Fish do not have eyes that are capable of seeing in the dark. However, fish have what are called photoreceptors. These are the cells that sense light from their environment. They move and react to these changes in light.

Do fish need and like darkness?

It depends on the species. Some fish prefer to remain in the dark, while others thrive in light. It is important to note that some fish, such as angelfish, are diurnal, meaning that they are active during the day.

Do fish need complete darkness to sleep?

Fish live in a watery environment, which means that they don’t need light to sleep. However, one study found that fish living in an aquarium lit at night with the frequency and intensity of moonlight did exhibit a significant decrease in activity and movement.

This suggests that lack of darkness may affect the animals’ circadian rhythm and may be affecting their sleep cycles.

Do fish like to sleep in the dark?

It’s a question that has haunted many a night. The answer is: it depends on the type of fish and its location in the water column.

Fish that live near the surface, such as tuna and mackerel, do not require light for sleep because light does not penetrate very far into the water. However, with most species of fish, lack of light means lack of sleep.


Fish sleep in the dark due to the fact that in the dark, they have fewer predators to worry about. However, if the fish is not comfortable with the dark, it may be necessary to provide it with an artificial light source or light source in order to have a good night’s sleep.


Artificial light at night interacts with predatory threat to alter reef fish metabolite profiles