Can I Use Blue Light In My Betta Fish Tank?

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Many fish owners wonder if they can use blue LED lights in their betta fish tanks. After all, how would it be different from using it in community tanks with many fish?

In this article, I will discuss whether it is okay to use this type of light with betta fish, how they will react to it, and how to do it properly.

So, without further ado, let’s dive right into it.

Even in dim, blue light, betta fish can still see their reflection.

Can I Use Blue Light In My Betta Fish Tank?

Yes, you can use blue light in your betta fish tank as it enhances their appearance and is harmless in moderation. While one study raised concerns about blue light causing stress in fish, moderation can avoid these side effects.

One study in the Fish Physiology and Biochemistry journal created some concern back in 2019.[1]

Jin Ah Song and Cheol Young Choi argued that blue light increased retinal stress in goldfish.

However, the research team recorded those results after elevating exposure time and light intensity.

But this is true for every color. You can harm most fish by raising the light intensity and exposure time regardless of the color.

In other words, you can avoid these side effects by applying moderation.

You will be hard-pressed to find anecdotes of people who harmed their betta fish after exposing them to moderate quantities of blue light.

Have you noticed that many of the restaurants you visit have aquariums with blue light?

Naturally, the goal is to enhance the fish’s appearance as opposed to boosting their health. This is true for private aquarium owners as well.

M.H. Amiri and Huda M. Shaheen noted in a paper in Micron that aquarists use various breeding techniques to enhance the color intensity and patterns in male bettas to make them more attractive.[2]

This shows you the critical role a betta’s appearance adds to its value.

Aquarists won’t hesitate to boost a fish’s appearance by adding blue lights, especially at night when they can’t rely on sunlight to view the aquarium’s contents.

If blue light posed a significant threat to betta fish, this habit would have faded. Aquarists in public and private settings would have replaced blue LEDs with a different color.

Blue lighting persists because the color is harmless in moderation.

Also Read: Facts About Bettas

Betta fish may enjoy blue light as a means of transitioning from day to night.

Do Betta Fish Like Blue Light At Night?

To understand the debate surrounding blue lights and their use in aquariums at night, you need to understand the relationship between betta fish and light:

  • Need vs. Want

Do betta fish need light? No, they don’t. In other words, you won’t harm your bettas by removing the tank’s blue LEDs.

Keep their origins in mind. Bettas in the wild live in Vietnamese rice paddies.

They are accustomed to muddy water, which creates a dark or dim environment, yet they thrive.

Bettas don’t need light. They can survive in a dark aquarium. However, that doesn’t mean they want to live in total darkness.

For their mental well-being, you should give their tank a few hours of light every day. The benefits are not that difficult to understand:

  • Jake A. Gerlovich from Drake University published a paper claiming that low light levels inhibited growth in Bettas.

Gerlovich and Gene A. Lucas highlighted the fact that some fish could survive in the sewers of Guadalupe, showing an excellent tolerance for polluted water.[3]

And yet, they only hinted at an inhibition in growth in the presence of lower light levels.

  • Light influences a fish’s circadian rhythm.

Irina Zhdanova (BioChron) and Stephan G. Reebs (Universite de Moncton) published a study on the subject in ‘Fish Physiology: Behavior and Physiology of Fisheries.’[4]

Their data showed that fish rested in constant darkness. Without that rest, they manifested lower locomotor activity.

You need a mix of light and darkness to maintain a betta’s well-being.

  • Light stimulates fish. They are more likely to eat, especially since food is easier to see and hunt.

These three factors create a contradiction. On the one hand, low light levels are a threat to fish. You could argue that blue is a low-light color.

But as was mentioned earlier, increasing blue light intensity and exposure will harm the fish. Therefore, you can’t respond to the dimness of a blue LED by increasing the intensity.

On the other hand, bettas live in dim environments in the world. They will also benefit from a period of complete darkness. The darkness allows them to rest.

But doesn’t that mean blue light at night is terrible for bettas? Well, it depends:

  • Some aquarists keep their blue lights on all night, and yet their fish sleep soundly.
  • In other cases, the fish wake up and emerge from hiding when the aquarist activates the blue LEDs.

You should approach things on a case-by-case basis. Does your betta flare at the glass walls when you turn the blue lights on?

Have they manifested additional signs of stress, such as a loss of appetite and lethargy? If so, cut back on the blue light.

Some bettas prefer a few hours of blue light before you expose them to 8-12 hours of darkness for the night. Others don’t want the blue lighting at all.

They want to remain in the dark once you turn the conventional aquarium LEDs off. They don’t need a moment to transition from day to night.

You also have bettas that only respond negatively to blue light because they need a few days to adjust the color.

You won’t know until you experiment.

How Do I Properly Use Blue Light In My Betta Fish Tank?

Your biggest concern is the duration. Bettas are unique because low light conditions may not produce the drastic side effects people typically expect to see.

After all, they live in dim environments in the wild. Therefore, you don’t have to torture them with several hours of intense blue light to see how they respond.

They won’t complain if the blue LEDs are barely bright enough for you to see the fish. The duration is the deciding factor.

If blue is the only color you have, aim for 8 to 12 hours of blue light each day. If you have other colors, including white, turn the blue color on between 6 pm to 11 pm.

If you only use the color to transition the fish from day to night, switch the blue LEDs off before you sleep.

You can also transition them to daytime by switching the blue lights on when you wake up. This practice also applies to other creatures, including aquarium shrimp.

Excess light is bad for the aquarium. Besides generating stress in fish, excess light will cause algae to grow uncontrollably. The same is true for aquarium plants.

What Is The Best Color Light For Betta Fish?

Bettas will respond positively to white LEDs because they mimic the sun, and the sunlight is good for bettas.

A study from zootechnics students at the Federal Rural University of Rio de Janeiro noted that exposing bettas to sunlight daily stimulated the production of vitamin D.[5]

Therefore, you can’t go wrong with a white LED, especially since direct sunlight raises the temperature and boosts algae growth.

Artificial white lights are the next best thing.

But because white lights are too bright for fish at night, many aquarists prioritize red and blue because both colors are beneficial for aquarium vegetation.

Can Betta Fish Sleep With Blue Lights On?

It is highly unlikely that your betta fish will be able to sleep if you leave the blue lights on at night. Betta fish can see the dimmest lights, even if they are blue.

Evidence of this will be flaring. If you are able to see your betta flare up when the blue lights are on, he is probably seeing his reflection and not sleeping.

Therefore my general recommendation is to use this type of light only as a transition between day and night. Don’t leave it any longer than that.

Some would argue that fish can sleep with blue lights, because the moon doesn’t go out at night, and blue lights mimic moonlight. But that’s hardly true.

Even in the wild, fish find their darkness when they go to sleep. They usually do this by getting close to plants and rocks. The same thing happens in home aquariums.

Also Read: Why Does My Betta Fish Stare At Me?


There is nothing wrong with using blue lights with betta fish. The best practice is to use this type of light as a transition from day to night.

You can switch the light to blue for an hour before bed. Make sure you don’t leave the lights on all night though, or your betta won’t be able to sleep.

It’s also a good idea to see how your beta behaves with this new habit. If it flares a lot and looks stressed, you’ll probably do better with plain white lights.