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Can Fish Sleep With The Aquarium Light On?




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As a beginner to fish keeping, you may have many questions about the lighting in your aquarium.

Which lighting color is best? How does the lighting help the fish? Will my fish sleep well with the aquarium lights on?

We’ll explore the answers to your lighting questions.

Is Lighting Important?

All creatures do best in their natural habitat. Since your fish keeping hobby is about creating a home away from home for your fish friends, the lights help create a natural environment.

The lighting allows the fish to thrive in the tank. Not only that, but it also creates an ambiance that brightens the fish tank, livens it up, and improves its aesthetic appeal. 

Fish tank lighting also helps the aquatic plants get the energy they need to grow and thrive, creating a good ecosystem in your tank, allowing both flora and fauna to thrive.

Can Fish Sleep With The Light On?

Like humans, most fish stay awake during the day and sleep at night. Just like they would in nature, fish need some darkness to sleep well. Fish can sleep with the light on, But they may not rest as well as they should.

However, the ability of your fish to get adequate sleep also depends on the color of the lighting.

Blue lights give the appearance of natural moonlight. Thus, the fish are more likely to sleep through the night with a blue light on as it mimics the natural habitat better. 

On the other hand, red lights give the same bright effect as the sun would. Therefore, fish may find it harder to sleep with the red light on. 

wonderful Fish sleep in aquarium
This saltwater fish clearly likes to rest with the lights off

For this reason, you should not leave aquarium lights on all the time unless you have the right lighting.

It helps to switch off the lights at night to allow the fish to get some rest.

Also, leaving the light on all day and all night will cause aquatic plants like algae to grow too fast, disturbing the tank’s natural ecosystem.

Any interference with the ecosystem may affect your fish. 

How long you leave the light on will depend on the fish you have. For example, with tropical species, 50% light and 50% darkness will best recreate tropical conditions.

For saltwater breeds, up to 10 hours of light may be enough to simulate the right aquatic conditions. 

What If You Switch The Light Off Completely?

If you’re planning to save on electricity by keeping the lights off, it might not be a good idea. You need some light in your aquarium for many reasons.

For starters, you won’t be able to see the fish. It’s no fun keeping fish if you can’t really see them, right? Also, you won’t be able to detect any problems with the fish.

Secondly, biologically, all plants and animals, even in the water, need some light. 

So depriving them of all light may cause them to die.

Thirdly, you need the light to check on the cleanliness of your tank. Fish thrive better in a clean environment. 

aquarium with fish with glowing yellow light

Finally, fish keeping is all about maintaining a habitat where your fish can thrive. Total darkness does not support the habitat. That’s because the light assists the plant life to grow.

Plants help in the absorption of waste products like carbon dioxide and ammonia and produce the oxygen your fish needs to get energy.

With that in mind, it’s not best to switch the light off completely. Fish need both light and dark periods to regulate their sleeping habits. 

Which Lights Are Best For The Fish Tank?

Compared to fluorescent and incandescent lighting, it’s best to use LED light for your aquarium.

LED lights are long-lasting (one bulb can go for 50000 hours), use less energy, and won’t produce too much heat, affecting the water temperature.

The lights also help to improve live plant growth. On top of that, they provide the right amount of lighting- sufficient but not too bright. 

The initial cost of LED lights may be more expensive, but they make up for it in the long run.

If you use a light that’s extremely bright, the fish will hide in the plants taking away from the beauty of your aquarium. 

It’s also essential to choose the right color temperature. The sun’s color temperature is 6700k.

Therefore, picking a color temperature from 6700k works for most aquariums. However, it’s advisable not to go beyond 10000k. 


It’s best to avoid having your fish tank lights on 24/7 as it throws off the balance of life in your aquarium.

Give your fish periods of darkness and light to mimic their natural habitats. This is best achieved with an aquarium light timer. Enough sleep will allow your fish to thrive.

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