Do Bettas Like Sunlight?

Since betta fish have always been raised with artificial light, do they even like real sunlight? Or does it hurt their eyes? Does sunlight even have an impact on the tank, and if so, is the impact beneficial, neutral, or even harmful?

Depending on where you buy your betta fish, they may have been raised outdoors, where they would only experience natural sunlight and no artificial lighting whatsoever. Betta fish do enjoy natural sunlight, though artificial light is a good alternative. One benefit you get from sunlight that you do not get from artificial light is that sunlight cannot be turned on suddenly and cannot harm your betta’s eyes.

In this article, we will discuss windows, eyes, pearling, 12-hour days, algae, and the natural habitat of betta.


When positioning your tank in your house, most guides about setting up your tank include a discussion about windows. This is due to the fact that if you move your tank near a window it will receive direct or indirect sunlight. The sunlight may cause some issues later on for reasons we will discuss here.

Not only do bettas love natural sunlight, but it is also possible for you to set up a tank without an aquarium light. You will need natural sunlight, so the tank will need to be near a window, but not directly in front of one. This will help you save money on your tank, as aquarium lights can be quite costly.

This will be most beneficial to you if you have low light in medium light plants. These plants will be able to thrive and grow at rapid rates using just the natural sunlight, without any expensive aquarium light being required.

However, unlike with a normal aquarium light, the plants will not grow directly upwards. Instead of they will grow in the direction of the sunlight, which can be used to your advantage, or it could be detrimental to the overall aesthetic of the tank.

for example, if the light is facing the front of your tank the plants will continuously grow forward and could block the view of one another. On the other hand, if the light is facing the side of the tank, everything will grow sideways, and while some in the back may have light blocked from them, it can create an interesting movement design.


Most people know that bettas are carnivorous, and they are in fact a sight-based predator. They rely heavily on their eyes and use them to hunt down their prey. Therefore, their eyesight is phenomenal, similar to ours, and they are able to detect every color that we can.

However, unlike our eyes, they are unable to adjust their eyes to different levels of light quickly. This means that suddenly flipping on the aquarium light may cause your betta to become blind over time.

When you use a natural like such as the sun, this cause of blindness is not a risk, as they are accustomed to changing their eyes as fast as the sun rises and sets. This is what they were evolved to do, so it is easiest for them to take the 30 to 40 minutes to adjust their eyes to various levels of lighting.

Almost all bettas are able to adjust to artificial light, but it will always be easiest for them to adjust to natural lighting. If you do not have natural sunlight lighting the tank, it is best to turn on the ambient light in the room 30 minutes to an hour before turning on the tank light.


Pearling is a phenomenon that most people, especially those with tank lights and low light to medium light plants, have not experienced. However, if you take those same low light to medium light plants and place them in direct sunlight for several hours, you will notice them pearling.

So, what is pearling? Pearling occurs when a plant receives excess amounts of light, carbon dioxide, and other nutrients, and is able to produce excess oxygen. This excess oxygen comes off of the aquatic plant in the form of bubbles. These bubbles look like tiny pearls, hence the name, “pearling”.

These tiny bubbles are basically pure oxygen, so these bubbles diffusing into the water greatly help your fish for a brief period, though it is not necessary for the longevity of your tank.

While it is possible to achieve pearling in high light environments, the necessary lighting units often cost well over $100, while the sunlight is free. This will help your plants grow faster, though note that they will use more nutrients. This could be good if you have an excess of nitrates, though you may need to fertilize extra.

12 Hour Days

Most aquarium lights are only supposed to be used 6 to 8 hours a day in order to prevent algae growth. However, there are very few areas in the world that consistently get 6 to 8 hours of sunlight every day. For example, the natural habitat of the betta gets about 12 hours of light daily.

If you want to set up a tank using only sunlight, not only is it more economical, it is also much closer to that of what betta would naturally experience. While the betta you are buying is likely multiple generations removed from its natural habitat, they still have natural instincts that are hard to override, and their circadian rhythm may be one of them.

It is possible that keeping bettas in conditions as close to their natural habitat as possible will make them healthier and happier. While there is not any research or evidence backing this up, it can’t hurt to try, and it will be much cheaper for you. In addition, you can grow plants faster and more effectively.

Bettas love to frolic in and out of plants, and while it may be tempting to simply buy an aquarium light that is rated for plants, you may want to try natural lighting first. If you happen to have a tank that is very close to a window and receives direct natural light, and you have a light for the tank, you should not use both lights.

Even though good, strong, lighting can make plants pearl, excess lighting will only help algae. Plants can only take in so much lighting, and if there is more light than they can absorb, the algae will use the rest.


The primary issue with the tank that has indirect or direct sunlight is algae. While plants can utilize the natural sunlight very well, algae can utilize it even better, especially after it has passed through a window. This can very easily lead to a massive algae problem that could destroy your tank.

However, there are some easy precautions and steps to take if you start seeing any algae in your tank. For one, close the window for a day or two. Blackouts take care of most algae. While it may be reoccurring, it is often easy to solve by simply blacking out the tank for a day or two then re-opening the window.

If you already have an algae problem in the tank, it is a terrible idea to switch to natural sunlight. These algae were likely caused by some other imbalance, whether it be nutrient, fertilizer, or other. Switching to natural lighting will only exacerbate the issue.

Natural Habitat

While we have mentioned that betta fish receive 12 hours of natural lighting in their natural habitat, they do not receive full direct lighting for most of the time. This is due to the fact that they are very small fish, so they spend a great majority of their time hiding.

If your tank is bare, plain, and you have glaring sunlight on it for 12 hours a day, your betta fish will become very stressed and anxious, as it feels it will not be able to hide from predators. On the other hand, if you happen to have a well-planted or well-decorated tank, feel free to give it 12 hours of sunlight. This will not only replicate your betta’s natural habitat, but it will also make your betta feel very happy and secure.

In conclusion, betta fish do enjoy natural lighting as long as they are also able to hide. They typically receive 12 hours of light a day in their natural habitat, though you may not be able to replicate this in a home environment, due to algae growth. It is also possible to set up a beautiful planted betta tank without using or buying any aquarium lighting, and instead opting for the sunlight option.

Leave a Comment