Should I Have To Keep My Aquarium Lights On 24 Hours?

Have you just bought an aquarium along with some adorable fish and now wonder if you should keep the aquarium lights on 24 hours?

Here’s your answer:

No. You don’t need to keep the aquarium lights on 24 hours because fish, like all other living beings, also need a good night’s sleep. You should switch the lights on for around 8-10 hours a day to imitate the rising and setting of the sun.

You should also keep in mind the type of fish and plant in your aquarium, and their specific lighting requirements when deciding on how long to turn your aquarium lights off.

How long should I keep my aquarium lights on?

Aquarium lights serve a few different purposes. They provide your aquarium with enough light to view your fish and their activities. They also give aquarium plants the much-needed brightness to grow and flourish.

Also, and more significantly, aquarium lights are responsible for providing your fish the natural environment they originate from, which means aquarium lights play a critical role in keeping your fish healthy and happy.

Now the question is:

How long should I keep the aquarium lights on? Ideally, it depends upon the kind of fish you own as a pet. Some fish require more lighting than others. Fish that originate from lakes and rivers are used to brighter, more intense light than fish from deeper waters.


When deciding on the hours for switching your aquarium lights on, you should consider the requirements of the different fishes in your tank.

Related: Is My Fish Pregnant, Fat Or Just Bloated?


Your aquarium lights are going to be affecting the aquatic plants inside the tank. It will come as a surprise, but the plants inside your aquarium may need light more than the fish. So you might also have to keep the light requirements of your plants in mind before you decide on a schedule.  

Fun Fact: Did you know that goldfish lose color over time if you do not provide them with the required amount of light? Slowly their color may fade, and they can turn white!

Check out this easy and simple aquarium lighting tutorial:

How does aquarium light affect the health of my pet fish?

How do you feel when you get a terrible night’s sleep? In the mood to kill, right? Similar is the case with the fish in your tank! A reasonable and sound resting period is crucial for the healthy functioning of all living beings.

It is important to note:

That your pet fish are also living beings that have a waking and sleeping pattern, which you need to keep in mind before setting up their living space, i.e., the aquarium. According to a study, fish follow a circadian rhythm for their daily functioning. Hence, this makes scheduling the aquarium lights all the more necessary.

In case you fail to switch off the lights, you will notice a massive change in the behavior of your fish. They will get sluggish, agitated, or may even stop eating.

It is because:

The constant lighting will not give them a resting period, and without sleep, they will get excessively tired and exhausted. You honestly don’t want to do that to your fish now, do you?

What is the Circadian rhythm, and why is it essential for aquarium lights?

Circadian rhythms respond to the light changes in an organism’s surroundings. It refers to the behavioral, mental and physical changes that happen in response to the light changes. All living beings have in-built biological clocks, which you can also identify as the wake-sleep cycle.

If this cycle disrupts, living beings can show signs of stress and agitated behaviors. Disturbed biological clocks can have negative impacts on the circadian rhythms, which in turn can have massive effects on the daily functioning of a living organism.

It can disturb their eating habits, hormone release, digestion, body temperatures, and other bodily functions.

This means:

You must keep a strict routine of switching the lights on and off during specific periods. You can turn the lights off when you go to bed and turn them back on when you’re up. It will give your pet fish an ideal resting period of around 8-10 hours, which is perfect for healthy, happy fish!

Have a look at this informative video about ten different freshwater fish you can keep in your aquarium:

But what happens if I turn my lights on 24 hours?

You should expect:

Your fish to turn into murderous monsters and a whole lot of algae growth!

Now you ask:

What are algae, and why is it wrong for your aquarium to have it? Algae is the slimy, greenish growth inside your fish tank. Algae growth is one of the most common problems you will face as an aquarium owner. Several factors cause algae, and inappropriate lighting is one of them.

Yes, it is true!

Excessive lighting can cause an outburst of algae in your tank! The algae growth can affect the health of your fish and the plants inside your tank. Therefore, it is not something that you should ignore. Since algae need photosynthesis to grow and flourish, lighting plays a significant role in its production. If you turn on your aquarium lights 24 hours, this means algae will get an ideal breeding ground.


Since your fish will not get the right amount of sleep, they will show signs of agitation and frustration. It may affect their health in the long run.

It is the reason why:

The ideal timing of switching on the aquarium lights falls between 8-10 hours.

Watch this video to learn some basics about how to keep your aquarium squeaky clean:

But what if I forget to turn the light off?

Well, that’s not a huge problem. One off incidents are okay, but if you are in the habit of forgetting, you should look into getting your tank a light timer. Light timers allow you to schedule the time when the aquarium light should be off and when it should turn on.

It will be super helpful since it will help maintain a strict routine for your fish, and their wake-sleep cycle will stay on point.


Light timers relieve you of the hassle to remember to turn the light on and off every day and night. It will also avoid situations where you forget to turn the light off and end up letting the fish suffer through a rough night.

Related: Small bubbles all over the tank – Why? What to do?

Now that we are clear on how long you should switch your aquarium lights on, one other vital issue to keep in mind is:

The type of lights you use for your aquarium

Lights also produce heat, and since your fish need warmth as well, they might prove helpful.


Once you start switching your lights off at night, you will have to find alternate heating techniques since some tropical fish need warm water to survive.

You will also need to make sure that your lights do not overheat the aquarium environment since that will also negatively impact the health of your pet fish and plants.

To help solve this problem:

You can look into getting ceramic bulbs for your aquarium, which will only provide heat to your tank without producing any light. These bulbs are an ideal alternative to heat providing aquarium lights.

So, how helpful did you find our take on answering your valuable questions? Drop your comments below and help us know!

Related: Where Should Aquarium be kept in the House?

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