Betta Fish Light – On Or Off At Night?

Last Updated on 2023-09-09

So you’re asking yourself the question: “should I leave my betta fish light on or off at night?”

The short answer. Off.

But, if you want to learn more about your betta, such as:

  • The dangers of having too much light or not enough.
  • Why sunlight may not be as good as you think.
  • How long you should leave your light on for.

And much more, then keep reading to find out!

Do Betta Fish Need Light At Night? The Short Answer!

Betta fish don’t need light at night. In fact, betta fish need 8-10 hours of darkness a day for their circadian rhythm to work properly. If a betta doesn’t get a break from light, it can result in stress, a lack of appetite, and an increased chance of sickness.

Do Betta Fish Need Light At Night? The Long Answer!

To understand WHY you should turn your bettas light off at night it helps to understand their natural habitat. You see, bettas live in rice paddies and river basins around South East Asia. As you can imagine, these basins are often much more shallow than other tropical fish are used to.

In fact, in the summer months, the basins and rivers can often evaporate completely meaning bettas have to jump from one small puddle to another!

The point is, while a betta fish may live in areas that are thick with vegetation; they also live so close to sunlight they have a day/nighttime cycle. Or in other words, they like to sleep when the sun goes down and wake when the sun comes up.

So as you can probably guess, if you start leaving your bettas light on OR off for too long, then it can have drastic consequences.

What Happens If Your Betta Gets Too Much Light (Or Not Enough)?

Now you know that betta fish need both light and darkness to thrive; you may be wondering what happens if your betta is getting too much light or not enough. Well, there are a few things that could end up happening.

Too Much Light

If your betta gets too much light it could result in:

  • The most common thing that is going to happen if your betta gets too much light is overstimulation. Without knowing when to rest your betta will be active all the time. This can result in them becoming stressed and agitated.
  • Another problem that can result from too much light is that your fish may stop eating. This could be due to the stress and overstimulation, or it could also result from your betta finding it hard to know when feeding time is going to happen.

In short, too much light is going to wreak havoc on your bettas body clock.

Not Enough Light

But what happens if your betta isn’t getting enough light?

  • If your betta doesn’t get enough light then they can often lose their beautiful coloring. Instead of looking healthy and vibrant, they may begin to look dull and weak. (However, other factors can cause this as well, such as PH level, algae bloom, and temperature).

Now that you’re getting a better understanding of whether you should leave your betta fish light on or off at night; wouldn’t it just be easier to use natural light?

betta care facebook group

Why Not Sunlight, Instead Of Turning A Betta Fish Light On Or Off At Night?

While some people may consider using sunlight for their betta tank, there are some drawbacks that need to be considered.

The problem with sunlight is that you don’t have much control over it OR the effects it’s going to have on your tank. In fact, too much sunlight can lead to bad consequences.

  • One of the main problems with sunlight is it could cause an algae bloom. Not only is an algae bloom going to reduce the visibility of your tank, but it can also affect your betta. An algae bloom can often result in bacterial infections such as fin rot, columnaris, dropsy and Popeye.
  • Another problem that you may not have considered is the effect on temperature. If your tank is in the sun all day it could cause the temperature of your bettas tank to rise uncomfortably or dangerously high. Causing stress in your betta and quite possibly death.

You Should Use An Artificial Light Instead!

Instead of sunlight, it’s a lot safer to use artificial light.  Unlike sunlight, artificial lights are MADE for your fish tank and aren’t going to affect the temperature of your tank; or produce as much algae compared to sunlight. And if you’re worried about forgetting to turn your betta fish light on or off at night, then don’t! Because nowadays you can even get automatic lights that turn on and off when you want.

And Remember…

You’re not going to need an overly powerful light for your betta tank. As an old rule of thumb, you should aim for 1 watt per gallon or below for LED lights and 1.5-3 watts per gallon for fluorescent lights. However, if you’re not sure, your best bet is to go into your local pet store and simply ask a professional to guide you!


When you’ve installed your artificial light there is one thing you’re going to need to watch out for. Sometime’s artificial light can cause your aquarium to reflect in on itself. Because of this, your betta may begin to act in an aggressive manner, thinking its territory is being threatened. If you notice your betta showing aggressive behavior then you may need to buy a weaker light OR find some way to stop the reflection occurring, such as:

  • Only turning your aquarium light on when the room light is on. Your betta is most likely to see himself when your tank light is on but the room light is off.
  • Another thing you can try doing is introducing the light to him slowly. Turn it on for a couple of hours a day, and then gradually increase it until it’s up to 8-12 hours and he’s showing no aggressive signs.
  • Lastly, you can also try placing aquarium paper on the outside to help darken your tank.
betta fish light on or off at night

How Much Light/Dark Does Your Betta Need?

When considering how long you should leave your aquarium light on and off for, you’re going to want to mimic a bettas natural environment as much as possible. Unlike our days, a bettas day can often be shorter (remember, dense vegetation can often block out more sunlight). Because of the amount of light your betta needs a day can range from 8-12 hours, and the amount of darkness it needs can range from 12-16 hours a day!

Make sure to join the Facebook group, where you can ask all your questions and show your betta!

To Recap

Now you should have a solid understanding of whether to leave a betta fish light on or off at night! And of course, the answer is off! And the most important things you need to remember are:

  • Too much sunlight can overstimulate your betta, causing stress and agitation, as well as possibly causing feeding problems.
  • If your betta spends too much time in darkness it could lose its color.
  • You should avoid direct sunlight in your tank and opt for an artificial light instead.
  • Too much sunlight can heat the water of your tank up to uncomfortable or dangerous levels, and it can also increase the amount of algae which can cause bacterial infections.
  • Your betta has a day/night cycle it follows just like you. You should aim to give your betta 8-12 hours of light and 12-16 hours of dark per day.
  • If you notice your betta is acting in an aggressive manner when the light is on, then it could be because he is seeing his own reflection. In which case, you need to find some way to stop this behavior.

Looking for a comprehensive guide about how to take care of your Betta fish? Click here!

If you want to check out more articles then here are some great places to go:

  • Do Betta Fish Need A Heater? – You may have been told that bettas don’t need heaters, and in some cases that can be true. However, in other cases, it can be fatal. Don’t risk your betta’s health, find out when you need to get a heater for your betta and what to do if your heater breaks.
Tropical Fish A-Z
Ultimate Betta Fish Care Guide
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