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Do Betta Fish Like Light And Should They Be On At Night?

The right lighting in your betta tank can really show off your fish’s beautiful colors and finnage to the best effect, as well as creating a relaxing ambiance in your room.

But what about your betta’s wellbeing? Should you put your betta fish light on or off at night? And, why is using sunlight to illuminate your betta tank, not such a good idea?

In this article, we reveal the dangers to your betta of having too much light or too little of the right kind of light, and much more.

Do Betta Fish Like Light And Is It Necessary?

As with all aspects of fishkeeping, you should try to replicate the natural conditions in which the fish live. That’s the best way to keep your fish happy and prevent them from becoming stressed and susceptible to disease.

Light And Dark In The Wild Environment

Yellow Betta fish in black background.

Wild bettas come from the Mekong and Chao Phraya river basins in Thailand, where they inhabit shallow bodies of water, particularly marshes, rice paddies, and floodplains. During the dry season, betta fish live in puddles, surviving by eating insect larvae and water-bound insects that alight on the water surface.

Most of the betta’s habitat is naturally dark, largely because of the dense aquatic vegetation that grows there and the fact that the water is muddy and often stagnant.

However, betta fish are surface feeders, and they can also breathe air when they need to by using their labyrinth organ. That means that bettas are usually found in the upper area of the water column, where it’s relatively bright with natural sunlight.

Wild bettas are most active during the daytime, finding their food by sight. When the sun goes down, and the environment becomes dark, the fish go to sleep.

In Captivity

Betta Fish swimming

In contrast, captive bettas are kept in brightly lit tanks so that their doting owners can view their fish’s spectacular colors and beautiful form. That’s fine for the fish, as they can see the food that they are offered, and, if they want to, they can escape the light and rest among the plants or caves in the tank.

However, just like their wild cousins, captive betta fish do need to sleep at night. So, you must turn out the tank lights overnight to replicate the natural day/night cycle that the fish enjoy in the wild.

The easiest way to do that is by turning the tank light on when you get up in the morning and switching it off when you go to bed at night.

When you go away, or if you work shifts, it’s useful to have a timer unit for your aquarium lights. Simply set the timer to switch the tank light on in the morning and turn it off at the end of the day.

Is Too Much Or Too Little Light Dangerous For Your Betta?

Aquarian fish swims in aquarium water

So, you now know more about betta fish light requirements.

But what happens to your betta if you leave the aquarium light on for too long or for not long enough?

Too Much Light

If your betta is exposed to too much artificial light, there are a few problems that could arise.

First, if your betta gets too much light, he may be overstimulated. Although bettas do tend to nap for short periods during the daytime, overstimulation causes your fish to be more active for longer. That can cause stress for the betta, which in turn leads to health problems and vulnerability to disease or attack by parasites.

Betta Fish Or Fighting Fish (Half Moon Double Tail) On White Background

Also, too much light can cause your betta to stop eating. Bettas can be picky feeders, and the stress of overstimulation often causes a poor appetite in these finicky fish.

Remember that betta fish are creatures of habit, eating during the daylight hours and sleeping when it goes dark. If your betta lives in an environment of perpetual daylight, his body clock won’t know when it’s feeding time, and he may stop eating altogether.

Not Enough Light

So, what happens if you deprive your betta of light?

Just as your betta tank should have a filtration system and a heater, it should also have lighting. If your betta is kept in very dim or dark conditions, he may lose some of his beautiful, vibrant colors.

Also, if you are hoping to breed from your betta, you should know that spawning is much less likely to happen in a very dark tank.

Why Not Use Natural Sunlight Instead Of Artificial Light?

Betta Fish swimming, with branch and plants

You may think that placing your betta’s tank on a windowsill or somewhere it will get plenty of direct light might be a good solution to your lighting dilemma.

Unfortunately, that’s not a good idea.

Here’s why.

Algae Bloom

Too much direct sunlight hitting your betta’s tank will encourage an algae bloom.

While algae are not dangerous to your fish, the green slime will quickly cover the glass, spoiling your view of your tank and making the whole environment look unsightly. Algae also grow on decorations, the substrate, your filter unit, and even all over your live plants.

The Betta Siamese fighting fish, Betta splendens Pla-kad ( biting fish ) Thai. (Halfmoon fancy white red betta ) in motion on fresh water weeds background

Algae are aquatic organisms that generate the nutrition they need through photosynthesis. Although algae are a nuisance, these organisms do have some benefits in that they remove harmful substances, including nitrates, from the water in your fish tank.

Also, any fish species, including bettas, pick at algae as part of their daily diet.

I keep algae growth controlled in my tanks by keeping algae eaters, including snails and Amano shrimp, both of which make good tankmates for bettas.

Temperature Shock

Bettas are extremely sensitive to temperature changes, and they can go into shock if the water in the tank becomes too cold or too hot.

If your betta tank is in a place where the sun shines on it all day, the temperature in the tank may become too high very quickly, which will definitely stress your fish and could even kill him.

How Much Light Does A Betta Tank Need?

Selective focus photo of blue betta fish on small glass container.

As a general rule of thumb, you should have 1 watt of light per gallon of water or less for LED lights, and 1.5 watts of light per gallon of water for fluorescent lighting.

In the wild, a betta’s day is generally shorter than ours. That’s because the dense aquatic vegetation in his environment blocks out much of the natural sunlight. So, to mimic that pattern in the captive environment, your betta should have between eight and 12 hours of light a day, followed by 12 to 16 hours of darkness to replicate nighttime.

What About Colored Lights?

Many aquarium lights come with a range of built-in color and special effect options, which you can use to great effect when designing your betta tank look and vibe.

Colored lights do not affect your betta any differently from white lights provided that you stick to the day/night routine.

Beware Reflections!

Fancy Halfmoon Betta on Black Background

Male betta fish are highly territorial and aggressive toward other males. The sight of their own reflection may trigger your fish to attack, mistaking his reflection as a male interloper.

Although your betta’s flaring might look impressive, it’s actually a very stressful experience for your fish. These tips will help to prevent reflections that artificial light sometimes causes.

  • Only turn on your betta tank light when your main room light is on. Reflections are most often caused when your aquarium is lit from within, and exterior lights are off.
  • Try introducing your tank light gradually to your betta. Turn the light on for a couple of hours daily, increasing that time until your betta remains calm and shows no signs of aggression.
  • Place aquarium paper on the outside of the glass to help prevent reflections inside.

If there’s a particular area in the tank where your fish flares or shows aggression, I find that placing a bushy plant in front of the glass often solves the problem.

Can Betta Fish See In The Dark?

The Types of Betta Fish: A Guide to Colors, Patterns and Tails : Three betta fish on black background.

As wild bettas live in a murky, dark environment, you may be wondering if your fish can actually see in the dark. To answer that question, you first need to understand a little about how the fish’s vision works.

Color Vision

Betta fish can see pretty much the same colors that you can, although it’s thought that the hues and shades that the fish see are slightly different from ours. Also, some bettas cannot see red light, and those individuals may, therefore, be described as colorblind.

Interestingly, fish that live in deeper water than bettas cannot see the color red. That’s because each color in the spectrum has a different wavelength, and water absorbs colors at different rates. Red is absorbed by water first, so species of river and deep-sea fish are unable to see the color red.

How Do Betta’s Eyes Work?

So, bettas’ color perception is very similar to yours, and there are similarities in the way in which their eyes work, as well as a few differences too.

Abstract close up art movement of Betta fish,Siamese fighting fish isolated on black background.Fine art design concept.

Bettas can focus precisely on a single object, which many other species cannot do. However, unlike your eyes, your betta will see an image that is blurry and contrasted, enabling the fish to differentiate the object extremely effectively through a high contrast image.

Blinded By The Light

Unlike you and me, bettas are unable to dilate and contract their iris quickly. It takes between 30 to 60 minutes for your fishy friend’s iris to adjust one way or the other.

That’s why you must never turn on your aquarium light without first switching on another light in the room. Suddenly switching on the tank light in a dark room could potentially damage your betta buddy’s eyes and may stress him.

Monocular Vision

Betta fish have monocular vision. That means that each eye sees a different image. Humans have binocular vision, meaning that you can use both eyes to focus on a single object.

Betta fish Fight in the aquarium black blackground

Creatures with binocular vision are likely to be predators and usually have their eyes facing forward. Animals with monocular vision are generally prey species and have their eyes positioned on the side of their heads.

Betta fish are predators, but they are also prey. So, while the bettas’ monocular vision helps them to stay alert for potential danger, the ability to focus on a single object enables the fish to be extremely efficient predators too.

Night Sight?

So, although your betta does have remarkable eyesight that helps to keep him safe from predators, as well as enabling him to hunt insects on the water surface, he cannot see in the dark.

Your betta friend can’t see in the dark, but he does have another amazing ability that helps him orientate and protect himself in his environment when the sun goes down.

Lateral Line – Your Betta’s “Sixth Sense”

Betta fish, siamese fighting fish, betta splendens isolated on black background

Look very closely at your betta, and you will notice a series of tiny holes in the scales that run along your fish’s sides.

The “lateral line” allows the betta to sense movement, vibrations, and changes of pressure in the water.

The fish uses that information to work out the size of an object in the water close to them, especially if that object is moving. The betta’s brain then processes that information to decide whether to flee from a potential aggressor or take evasive action to avoid bumping into something.

So, although your betta fish cannot actually “see” in the dark, he uses his amazing sixth sense to keep out of trouble and avoid colliding with the tank sides and structures within his environment.

Final Thoughts

Your beautiful betta fish has remarkable eyesight. He can see the same colors that you can, he can focus with deadly accuracy on his prey, and he uses his sixth sense to keep him safe in the dark.

Bettas need a clearly defined daytime and nighttime to be happy. Your fish will be busy feeding and exploring during the day while at night, your betta needs darkness so that he can sleep and rest.

If you provide your betta buddy with that, he will be a happy, long-lived fish.

Alison Page has been an avid fish keeper for over 35 years and has owned many different species of freshwater tropical fish including bettas. Currently Alison has two large freshwater tanks. The first tank has two huge fancy goldfish who are almost ten years old and still looking as good as ever. In the other, she has a happy community of tiger barbs, green tiger barbs, corydoras catfish, platys, and mollies.

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