How Much Light Do Betta Fish Need?- Dim Or Bright?

Aquarium light is probably the last thing you would worry about. After all, do little creatures like Betta care about lighting at all? Sorry to burst the bubble. But it’s a terrible misconception. Bettas do need light to live and thrive happily. But “how much” is the actual question here.

In the spectrum of high to low light, Betta surely prefers medium. The light should be bright enough to provide a clear underwater vision (to help hunting). Plus, overstimulating the fish’s nervous system shouldn’t be too bright. Having a balance is the key.

Now, you are wondering how to find the balance. We know it’s not easy, considering all the available options. But don’t worry. We have tried to give you the most hands-on article on this topic. Hopefully, by the end of this discussion, you will know the type, power, and color of your betta-tank’s light setting. So, don’t skip anything.

Key Takeaways

  • A healthy betta needs the tank to have dimmed lighting during nap time.
  • When it’s awake, the light must be turned on to imitate the “day.”
  • Betta needs 12-14 hours of light followed by 12-10 hours of darkness.
  • The thumb rule of having “enough brightness” is to make sure each liter of water has at least 20-25 lumens of flux.
  • A 4-watt LED light panel should be enough for your 5-gallon tank.
  • If the tank is planted, the light requirement will be much higher (almost 40-70 lumens per liter).
  • Planted tanks are encouraged to give bettas a nice hide-out place.

How Much Light Do Betta Fish Need Per Day?

It depends on your Betta’s sleep cycle. The main point is to keep the aquarium dark while the fish is sleeping. Now, some fish decide their sleeping time by themselves. You just have to keep track of their preferred nap time and dim the lights.

But some Bettas don’t like slowing down as long as there is light inside the aquarium. In that case, it’s better to artificially imitate the day and night cycle inside the tank. By that, we mean turning the lights on during the day and vice versa.

So, that gives the little fish 12 hours of brightness followed by 12 hours of darkness. Some people might want to stretch the daytime a little (14 to 16 hours), which is fine too. As long as you provide brightness and darkness in a familiar pattern, your Betta should be okay.

Having enough light is not just an option; it’s mandatory. Bettas are not deep ocean species. They live on the upper surface of narrow streams and puddles. The reason is having access to sufficient daylight. Yes, Bettas can’t see in the dark. To be able to locate and finally eat the food, the area must be bright enough. 

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The lighting cycle shouldn’t be an issue if the Betta tank is kept inside a room with access to a big window or balcony. However, the problem arises when the room lacks any of these facilities. You are entirely dependent on an attached aquarium light. We suggest getting a light controller that will automatically turn on/off the lights when it’s time.

Are LED Aquarium Lights Too Bright For My Betta Tank?

Aquarium lights usually come in small LED panels. But you can skip that if you find the light too bright. Go for a desk lamp with a halogen or incandescent bulb. It gives a yellowish hue instead of a cool tone. The problem with incandescent light is that it can be “too low” for a planted aquarium.

As we all know, plants need a good lighting source to continue photosynthesis and grow. Plus, Bettas do love lighting that helps them see the tank clearly. So, if you choose incandescent lighting, ensure the bulb can generate enough lumens. How much lumens are enough will be discussed below (in detail).

LED lights seem like a decent option to us. You can get them in any color you want. But we advise you to stay with warm white or red. Green is a huge No ( no matter how great it looks). It will stop the plant’s growth and might end up killing it. other than that, Bettas don’t have a preference for any color light. Just make sure it’s too bright or in the face.

Something too bright can increase the stress level, triggering frenetic behavior. You will see the fish swim back and forth as if trying to find a spot where it can hide. Bettas don’t have eyelids. So, the poor fish can’t even close its eyes when the light is blinding. Imagine sitting in a small room with ten LED light bulbs. It will tire you out even though you can close your eyes.

While we are fighting over LED and incandescent light, some prefer going all natural. That means putting the tank near a big window. You don’t have to create an artificial day and night cycle. The sunlight does it for you. However, the problem is that natural light can increase the water temperature. Plus, the brightness is out of your control completely. You have to always keep an eye on the weather temperature.

That’s why we believe using artificial light would save you from all the troubles.

gorgeous black betta
Owner: Jody Tourand

How Much Brightness Is Enough For A Betta Tank?

Bettas love a medium-light set-up. We have said it before. But that means you have to avoid both harsh and poor lighting. The issue with harsh lighting is that it scares the poor fish. In their natural habitats, betta fish always cover the surface with dry leaves. It makes them feel comfortable. Extreme lighting can do the exact opposite and increase the stress level.

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So, let’s find out what medium lighting actually means. Usually, 0.5 watts per liter is considered medium lighting. If it’s LED, you get around 20-25 lumens in 0.5 watts. For incandescent lights, the number is even lower (around 12-13 lumens). By nature, the lumen coming out of an LED light is more concentrated.

 That means LED is better at illuminating a certain portion of the room (or, in this case, a tank). On the other hand, lumens from an incandescent light tend to scatter around the entire area. that’s why it covers a large area. However, the area looks dimmed due to the low concentration of lumens.

Here’s a quick calculation. Suppose you need 20 lumens in one liter. Then, for 5 liters, it would be 378 lumens. All you have to do is look for an LED light that can generate at least 378 lumens of flux. Look at the table below. The closest option we have got is 375 lumens or a 4-watt LED light.

That’s how you decide whether a light is too bright or not for your respective betta tank. For example, a 2-watt LED light producing only 100 lumens is too dim for our tank. On the other end, a 9-watt LED light (800 lumens) would be too much, considering we only need 375 lumens. Easy, right?


That math was too simplified. In real life, most people use “Gallons” instead of “Liter” to signify their tank size. So, first, you have to convert your tank size from gallons to liters. Then, you can follow the previous calculation as it is. No worries, though. We have calculated the ideal light for some common Betta-tank sizes below. Hope it helps.

Tank Size (in gallon)Tank Size (in liter)Required lumensSuitable LED Light
2 gallon7.5 ltr1503-watt
5 gallon19 ltr3804-watt
10 gallon38 ltr7609-watt
15 gallon56 ltr112012-watt
20 gallon75 ltr150017-watt

There you go. Even if your tank size is unconventional (not mentioned here), you can still find the right amount of lighting. The rule of thumb is to make sure each liter of water gets at least 20 lumens. The requirement will be slightly different for fluorescence bulbs. Each watt of fluorescent bulb contains fewer lumens compared to the LED ones. It can cover more area, but the brightness in each liter of water will be medium to low.

rainbow color marbling betta fish
Owner: Frankie Hernandez

How Much Light Is Enough For A Planted Betta-Tank?

As you can see, we have only calculated lighting for a betta-only tank. However, many aquarists prefer decorating their tanks with herbs and plants. In that case, you have to consider the plant’s lighting needs, too. For example, Java moss, Anubias, dwarf aquarium lily, etc., are high maintenance, including light.

How much light each of these plants requires is a topic for another day. Just know that 40 lumens per liter is a good start for any planted aquarium. You might fall short if the plant is too dependent on direct light. But overall, 35-40 lumens per liter should be okay.

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Also, keep in mind to only get low-light plants for your betta tank. Bettas don’t behave well inside a “too bright” aquarium. It makes sense, considering the Wild-water habitats are full of attackers. A low-light setting makes them feel safer (easy to hide). You can try Amazon Sword, Java Moss, Marimo Moss balls, etc. They all look fabulous in a tank, providing the perfect hide-out for a shy Betta.

Here’s how much brightness you would need for a tank with plants that require low-to-medium light.

Tank Size (in gallon)Tank Size (in liter)Required LumensSuitable LED Option
2 gallon7.5 ltr3004-watt
5 gallon19 ltr7609-watt
10 gallon38 ltr152017-watt
15 gallon56 ltr224027-watt
20 gallon75 ltr300032-watt

Note: we have only used 2-gallons tank as an example. If you have more than one betta, 5-gallons is the minimal tank size. Anything less than that is not ideal.

blue white gorgeous betta fish
Owner: Sean Aurellio

Will My Betta Fish Die In Darkness?

The answer is both yes and no. Darkness is not a direct killer. No body parts of the Betta will malfunction if they spend an entire day in darkness. However, we highly advise you to avoid such situations. A betta needs light to thrive inside the fish tank. It is an extremely important part of their daily activities. Bettas depend on a light source to tell the difference between daytime and nap time.

Without light, their daily sleeping cycle gets disturbed, triggering stress and lethargic behavior. So, how long can a Betta live without light? If you mean no light (pitch black), the fish can survive until its stored energy drains out. There’s no way a betta can locate food without any light.

So, it has to starve itself until the lights come out again. Suppose a betta can last 7 days without eating any food. That’s how long it can survive in a dark tank. Once the period ends, they stop looking for food and just shut their bodies. It’s called going into hibernation.

The good thing is bettas can fast for 10-12 days. In the meantime, they use all the fat stored in their body to perform daily activities. After one week, the fish starts going into hibernation mode. It helps them save some of the energy still left in them. But what’s after that? If you still don’t help the poor fish by turning on the lights, it will slowly get sick and eventually die. It only depends on how long the body can survive without food.

You see, it doesn’t happen overnight. The process can take much longer if your fish is skilled in finding food, even in the dark. But that’s rare.

Before You Leave!

No matter which light you choose, it all comes down to the day & night cycle. You have to know when is the right time to turn the lights on and off. Since light is one of the most crucial elements in a Betta’s life, you can’t leave room for mistakes. To learn this matter more deeply, kindly follow our article on “betta fish lighting cycle.” It explains everything from a perfect light set-up, circadian cycle and effects of not having enough light per day.

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Muntaseer Rahman

About Author

Hello, I’m Muntaseer Rahman, the owner of I’m passionate about aquarium pets like shrimps, snails, crabs, and crayfish. I’ve created this website to share my expertise and help you provide better care for these amazing pets.


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