Can A Light Be Too Bright For A Betta Fish?

Betta thrives when you successfully put it into a day-and-night rhythm. That means you are turning the light on, which imitates daylight and vice versa. Then, why is your Betta becoming grumpier by the passing days? You might have used a light too bright or harsh for their eyes.

Light can be too much for a Betta fish if you don’t consider the tank size and the bulb’s capacity. A tank consisting only of betta would require less brightness than one with both fish and plants. Staying under harsh lighting will eventually irritate the fish.

The list never ends when you start learning about Bettas. But you are giving so much effort to see your Betta healthy and happy. And that’s the whole point. So, without further ado, let’s learn how to calculate the right betta tank brightness.

Key Takeaways

  • Even though bettas live better under a daylight cycle, sometimes light can be too intense.
  • A 9-watt light bulb (LED) is too much for a 5-gallon tank.
  • The tank size matters a lot when deciding how much brightness is needed.
  • A 2-watt LED light is not bright enough for a 5-gallon tank.
  • Staying under harsh light can cause the fish to be overstimulated, anxious, and less interested in eating.

Do Bettas Need An Aquarium Light At All?

Yes, Betta or Siamese fighting fish need both darkness and brightness. The absence of brightness will abruptly stop the circadian rhythm they are used to. As you know, Bettas don’t have eyelids to shut off. They assume it’s day when rays of light enter their retina and vice versa. They can’t live without any trace of brightness for very long. We can prove it even by the natural habitat they choose in the wild.

They prefer puddles found in rice and paddy field or nearby a shallow stream. They usually spend most of their time on the top portion. You don’t have to look too deep into the pond to find a betta. They choose to live on the surface to have better access to natural light. It helps them target their prey better. Yes, Bettas are attackers and hunt for food every day. But unlike natural hunters, they have poor eyesight.

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By that, we mean they can’t see clearly if there is no light in the area. And they don’t have any other useful sense that would help them find insects even when it’s dark. So, they have to wait for light to find food. We guess it tells you exactly how much bettas need brightness.

colorful betta in planted tank
Owner: Logan Aikens

How Do I Know If A Light Is Too Bright For A Betta?

Bettas depend on light to live. But sometimes, it can be too intense. Their eyes are weaker than ours. So, even if we find a soothing light source, it might hurt the fish. But before we tell you how much brightness is okay for a Betta tank, you should be able to identify whether a Betta is bothered by the light or not. It makes total sense, right? So, here we go.

1. Lack Of Appetite

Overbrightness leads to overstimulation. It’s hard to believe. But staying under bright lighting for too long can suppress your Betta’s hunger. That means they wouldn’t find the food as appealing as they usually do. You can easily identify it by observing the amount of leftover food in the tank. You have something to worry about if it’s significantly more in number.

Not eating much also triggers tiredness and pushes the fish towards lethargic behavior. Considering bettas love being active and eating as much as they can, the sudden change indicates a stressful situation in the tank (brightness).

2. Moves Frantically

You see your betta move frantically inside the tank. It’s because bettas love a good “shadow.” Even in nature, you will see bettas choose to live in areas that are covered by dry leaves. It makes them feel safe. Once you turn on the light (too harsh), any feeling of safety disappears. They suddenly feel like they have nowhere to hide or be comfortable. The frequent moving shows how desperate the fish is to find a safe spot away from the light.

Guideline For Choosing The Right Lighting Set-Up For Bettas

Here is a cheat list to help you figure out which LED light bulb you should choose. We have only picked LED options because they seem to be more popular than anything else, like incandescent or UV light.

Tank sizeRequired LumensWatt (LED)
Small size (5 Gallon)3754
Small to medium (10 Gallon)8009
Medium to large (20 Gallon)160017
Large size (40 Gallon)300032

Your tank size is not mentioned in the table. No worries. We have explained the calculation later in this article. We promise you won’t end up with harsh lighting if you follow the numbers in this table.

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We have assumed you only keep bettas in the tank. If there are other species in the tank, it will slightly change the required brightness. That’s the biggest dilemma many betta-keepers face. It seems like Bettas doesn’t like harsh lighting. But some aquatic plants don’t grow well under dimmed light. Try to decorate your Betta tank with plants that can live without too much lighting.

Once you have decided how much brightness the tank should have, you can pick a lighting source.

gorgeous pink betta fish
Owner: Marleen Stegemann

1. Desk Lamp

If you are not too bothered to keep the tank fancy and all, just get a good-quality desk lamp. There’s a chance you already own such a lamp. You can use the switch to change the tone from cool to warm. Just place the head in a way that illuminates the tank water.

2. Led Panel

If your tank has a lid, it would be better to stick with LED panels. These panels have small micro-size bulbs attached together. Some of the bulbs might emit a bluish tone (just for variety). You can also decide how white or orangish the light should be. It’s totally up to you.

3. Incandescent Light

Fluorescent lights allow you to bring a “sunset” vibe into the room. One thing about an incandescent light bulb is that it illuminates more area than a LED light. The latter is more focused, while the incandescent ones are more spread around the room.

4. Natural Sunlight

The problem with natural sunlight is that it is out of your control. So, even if you sometimes let the tank enjoy sunrays, there should be some kind of backup. So that when it hits noon, and the sunlight gets hotter, you can close the window.

Is A 2 Watt Light Enough For My Betta Tank?

It depends on what else you have inside the tank. Does the tank only accommodate bettas? Or do you have aquatic plants as well? If yes, then your lighting requirement will be higher than a simple betta-only tank. Because bettas can adjust with low light, unlike a high-demanding plant. It would die without access to blue or red light (for photosynthesis). However, to keep the conversation simple, we assume you only have Bettas in the tank.

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A 2-watt LED light bulb is able to produce 100 lumens of light at once. On the other hand, a 9-watt light bulb (LED) produces as much as 800 lumens. For clarification, lumens mean the number of candles lit at once to replicate the brightness of the bulb (from a one-foot distance).

The next step is to figure out a tank size. Then, you can easily calculate how many lumens per liter you are getting. On this note, 20-40 lumens per liter is ideal for a betta tank. If it’s a planted tank, try to keep the number on the higher end.

Here’s a table to help you visualize the entire thing.

Tank sizeLumen Per Liter (2-watt bulb)Lumen Per Liter (9-watt bulb)
Small size (5 Gallon)100/(5×3.75) = 5.33 lm/ltr800/(5×3.75) = 42 lm/ltr

As you can see, 2-watt light bulb was too insignificant for even a small size tank. It might be alright if the tank size is less than 5 gallons. But we don’t recommend that. On the other hand, the 9-watt light bulb is too much (42 lumen per liter). The middle point would be 4-watt LED light which generates 375 lumens. It translates to 20 lumens per liter.

That’s exactly what you are looking for.

rainbow color marbling betta fish
Owner: Frankie Hernandez

What Color Lighting Do Bettas Prefer?

Not just the brightness level, you can also choose a color for the light. But it’s not mandatory. Bettas don’t care much about which colored light their tank has. However, if you want to make the lighting more suitable to your Betta’s liking, knowing the color theory might help.

Usually, LED panels come in white and blue light. They are the most common option. Both colors illuminate the tank to a great extent. Blue, as a color, has the tendency to overstimulate Bettas. White helps the Betta see its prey more clearly. But it can be too harsh sometimes.

Next, red is proven to lower the stress level. But you can notice sluggish behavior after a while. Finally, we have yellow. It gives a vague sunset vibe to the tank. By far, yellow lights have the best effects on Bettas since it replicates the light of their natural habitat.

BlueStimulates the mood significantly. Betta is more active in the tank.
WhiteHelps to see the tank better.
RedLow-stress level
YellowLooks the most natural

Before You Go!!

Bravo! You have finally figured out the right lighting setting for a Betta tank. But it will only be effective if you can run the day-night cycle well. To avoid making any mistakes, check our article on Betta’s lighting cycle. Hope it washes all your worries away.

Article Link: Betta Fish Lighting Cycle: How Long Do Bettas Need Light?

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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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