Does fish require light at night?

Do Fish Need Light at Night?
4 Min Read
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Aquarium fish require light at night, and it’s preferable to turn it off at night. Fish can become stressed if the light is left on since they require darkness to sleep. Algae will quickly grow and make your tank look dirty if you expose it to too much light. So, in a nutshell, no, you should not leave your lights on.

For fish owners in particular, it is important to know that they are taking care of their swimming companions correctly.

One of the most asked questions is whether Fish require light at night, so in this article we will be revealing all there is to know!

Should You Keep Your Aquarium Light on at Night?

The answer to the fish requires light at night question is not straightforward as there are many factors which come into play. It is not only about the environment or the amount of light but more so about the type of fish you have. 

Fish vary dramatically and require different needs, so it is important to do your research on the fish itself before going forward.

But despite this, many fish share the same type of vision which is enough to help us know fish require light at night?

A Fish’s Eyesight

Before going further, it is important to acknowledge the eyesight of the fish. It is known that a fish’s eyes are similar to a human’s in the way it is structured and how it functions, the only difference being the spherical shaped lens they have to allow them to focus in water.

What’s more is that they too have rod and cone cells – these are responsible for black/light and color vision.

As we have established prior, a fish’s eyesight still depends on the type of fish itself as well as its lifestyle. Whilst some prefer low light, others will benefit more from a bright light.

Because of this, there are ways to work around these differences if you happen to have an aquarium shared with multiple species of fish. 

Fish Require light at night Recommended

The most common fish for people to own is tropical fish and these fish, even though there are many species, will be able to handle a shared amount of light.

It is recommended that fish have between 8 to 10 hours of light a day, meaning that fish do not necessarily need to have any form of light overnight.

The easiest way to understand is to look at fish outside of the tank. Fish are not given artificial light but only natural light from the sun and the moon.

Because of this, they would have had to adapt to see underwater without light. If you turn off the light for your fish at night, they will be able to adjust and still swim and live freely within the aquarium.

Admittedly, the light we use for these fish tanks are more so for us to view the fish rather than for the benefit of the fish themselves.

Light Is Necessary

The reason we recommend between 8 to 10 hours of light a day for fish is because light is necessary. Although it is not needed 24/7 and they can function without, it is still important to provide light when possible.


One of the things that need to be acknowledged the most is the fish’s health. The amount of light a fish receives can have a major impact on their health, and this is something that is not acknowledged enough.

If a fish is kept in the dark for too long, this can make them lethargic. As a result, these fish will not consume enough food and then the sickness will finally settle in.


Did you know that most fish don’t have eyelids? It is normal for people to assume that fish do not sleep because all we ever see are wide-open eyes, but this is not true at all. In fact, fish sleep just like we do and it is important that they receive that rest. 

Because of this, it is important to fish require light at night out on your aquarium in order for them to get sufficient rest. It can be hard enough for us to sleep with bright light.

Imagine trying to sleep with light without eyelids! Again, lack of rest can be a cause for a lethargic fish which can lead to sickness and, in worse cases, death. 

Keep your fish happy – they are just as prone to stress as humans are, so keep this in mind.

Using a Night Light

Now that we have established that fish benefit from darkness, we can understand that they need their rest. But what does that mean for the owners? Many people have aquariums in their homes not only for the fish but for aesthetic purposes.

As you welcome guests into your home you want to be able to show off your tropical fish in all their beauty, but with the light off this cannot be accomplished.

If you choose to, instead of completely shutting off the lights you can instead put in a night light. Choose a light which is dimmed such as a calm blue.

By doing this, you will be able to see your fish and they will still get the much-needed rest they require. It may even make the fish feel more relaxed with a dull set tone.

Luckily, you do not have to worry about going out of your way to purchase a separate light for this. Many lights in fish tanks already come with alternate light settings for this purpose.

Final Thoughts

Overall, fish do not need light at night because it is important for them to be able to rest. There is a misconception that fish do not sleep but this is not true at all. Fish need plenty of rest in order to keep their energy. 

Without this energy they will not eat as much as they should which will eventually lead to illness. But, with this said, Fish require light at night.

As long as your fish sustain the correct dose of light and darkness, they will be comfortable and stay healthy.

Tyger Leader is reader-supported and may earn a commission when you book or purchase using our links. Learn more about our affiliate disclaimer here.

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