I get commissions for purchases made through links in this post. As an Amazon Associate I earn from qualifying purchases.

Should Aquarium Light be Left on at Night? (Answered)

Wandering, should aquarium light be left on at night?

Well, in this article, I am going to answer the same question.

I will also tell you other important things you must know when it comes to aquarium light.

So let’s dive into it.

So, should aquarium lights be left on at night?

You should not keep aquarium lights on at night because fish need darkness to sleep in the aquarium. Also, if you keep the aquarium lights on then the algae will grow rapidly in your tank.

Should Aquarium Light be Left on at Night? (Answered) image

Why you should not keep aquarium lights on at night?

There are a few reasons you should not keep the aquarium lights on during the night.

1. Fish needs darkness at night to sleep

Just as we do, fish also needs darkness to sleep properly at night.

In their natural habitat, there’s no light during the night time. So keeping the aquarium light on in your tank during the night can disturb their circadian rhythm which causes stress in fish.

You can easily identify symptoms of stress: 

  • If you notice your fish are constantly fighting with each other then it is a sign that your fish are stressed out.
  • If your fish are not eating properly i.e. they’re n]ot eating the amount of food they used to eat then this could a sign of stress.

These symptoms can get very severe over time. And it can even lead to the death of the fish.

Do Goldfish sleep? (Answered)

2. Emulate the natural habitat of fish

To keep your fish happy and healthy, it is always a good idea to emulate its natural habitat.

In its natural habitat, fish experiences day and night cycle.

So you should mimic the same in your fish tank.

And turn on the aquarium light during the day and switched it off during the night.

Nowadays there are some aquarium lights that can mimic the sunrise, sunset, and even moonlight in the aquarium.

These aquarium lights are fully programmable.

You can literally program them for 24 hours to mimic the sunrise, midday sunset, and even moonlight in your aquarium.

So if you use these aquarium lights then you can actually keep the lights on during the night. Because these aquarium lights can emulate the natural moonlight during the night time.

You can check out the 24 hours programable light at Amazon here.

However, you don’t need to have these lights in your aquarium. Any aquarium light can do the work.

However, there are a few advantages of using these fully programmable aquarium lights.

  • First of all, they look amazing which you can expect from premium aquarium light.
  • Another thing is as these aquarium lights emulate the sunrise and sunset, your fish will not get shocked as they do when you turn on and off the normal aquarium lights.

12 Benefits of Live Plants in an Aquarium (Pros and Cons)

3. Algae growth

Probably the most important reason you should never keep aquarium lights on at night is that it causes algae growth in the aquarium.

Algae basically require two things to grow in an aquarium.

  1. Nutrients
  2. Light

Algae can get nutrients from the ammonia produced by the fish in your aquarium.

And when you keep the light on for more time than necessary, it causes algae growth in your tank.

Now, you may be wondering, how much time should I keep my aquarium lights on?

I’ll answer that below.

How many hours a day should aquarium light be on?

fish tank with aquarium light on

Feature image – Author: Pete Brown Licensed by CC BY 2.0 Cropped and resized

An aquarium requires light anywhere between 8 to 12 hours every day.

As you can see, it is a wide range!

This is because it really depends on the setup of your tank.

Basically, there are several factors that come into play while determining how much time you should keep your aquarium lights on every day.

1. Live aquarium plants

One of the most important factors that come into play while determining the number of hours you should keep lights on in your tank is whether you have live aquarium plants in your tank or not.

And what type of aquarium plants you have in your tank.

If you have live aquarium plants in your tank then you may need to provide light it as much as 12 hours every day.

On the other hand, if you don’t have live aquarium plants in your tank then keeping lights on for 8 hours or even less is sufficient.

Aquarium light is very important for live aquarium plants because it helps them to create their own food by the process of photosynthesis.

But just because you can live aquarium plants you can’t just keep the aquarium lights on for 12 hours.

Because this my cause algae growth in the tank.

Does CO2 Reduce Algae in Aquarium? (Get Rid of Algae!)

So, how many hours a day should you keep the aquarium lights on if you have live aquarium plants in the tank? 

First of all, it is recommended that you should keep plants that are compatible with the environment of your fish tank.

For example, if you have a cold water aquarium then you should keep plants that can do well in cold water.

If you have a tropical aquarium then you should put the plants that do well in warm water.

And a general rule to follow when it comes to light for your live aquarium plant is as follows:

  • In a cold water aquarium, you should keep lights on for 8 hours on a daily basis.
  • In a tropical aquarium, you should keep lights on for 12 hours every day

Still, as I said earlier, how much time you should actually keep the lights on in your tank really depends on the setup you have.

On that note, you should start by keeping your aquarium lights on for 10 hours every day.

After a few days, if you notice a growth in your tank then you should reduce the light to 9 hours every day.

On the other hand, if you are providing 10 hours of light and you don’t notice any algae growth then you can increase light in your tank.

But remember that when it comes to aquarium light, you should never keep the lights on for more than 12 hours. 

Besides, as you increase light in your tank, you should also increase the fertilizer doses and CO2 injection (if you are adding CO2 in your tank).

52 Best Freshwater Aquarium Plants For Beginners (And Care Guide)

2. Fish in your aquarium

The type of fish you have in your tank is another factor you need to consider when it comes to lighting for your aquarium tank.

Generally, you can keep most of the aquarium fish in any lighting condition.

Usually, in the aquarium, fish gets more light than they get in their natural habitat.

And to the most fish, more lighting will not affect them too much if not at all.

However, there are some fish species like Tetras and Cichlids that, in their natural habitat, most of the time, live in darkness.

So these fish can get affected negatively if they are getting exposed to too bright direct light.

So if you have such species of fish in your tank then you should consider reducing the intensity of the aquarium light.

If for some reason, you can’t do so then you can create a lot of shade in the aquarium by adding ornaments and/or floating aquarium plants.

If you do this then the fish will get a lot of space to hide under ornaments and hide away from the bright light and feel secure.

A general rule to follow when it comes to light for your aquarium fish is

  • if you have tropical aquarium fish then usually in their natural habitat they are getting about 12 hours of flight every day. so you can do the same in your tank and provider of league hours of light each day to them.
  • if you have cold-water fish in your time then in their natural habitat the lighting usually very is according to the season. And in general, they don’t require longer light so keeping light about 8 to 10 hours every day is sufficient for such fish species.

Again, too much light is not going to bother most of the aquarium fish.

When it comes to light it is more for you than the fish.

You want good lighting in your fish tank because you want to enjoy your fish. 

So, as far as you are not going too far with the light, it is totally fine with the fish.

12 Best Freshwater Fish for Aquarium (5th is the Coolest You’ve Ever Seen)

3. Ambient light in the room

How much ambient lighting already present in the room where your aquarium is situated is also an important factor to consider when it comes to providing additional lighting to your aquarium.

If your aquarium is located in a well-lit room and has a lot of ambient light then you may not need to keep the aquarium lights on for 12 hours.

Keeping aquarium lights on for 8 to 10 hours every day will be sufficient.

Again, lighting is especially important if you have live aquarium plants in your tank.

So if you have some live aquarium plants in your tank and the aquarium is located in a well-lit area. Still, the ambient light is indirect so the plants can’t use them properly for the process of photosynthesis. So you’ll need to provide direct light to your aquarium plants through aquarium light.

Overall, if you have a lot of ambient lighting in the room then keeping the aquarium lights on for less time i.e. 8 to 10 hours every day is sufficient.

On the other hand, if your aquarium is not in a well-lit room then you may need to keep lights on for a longer time.

6 Tips to Take Care of Live Plants in Aquarium (For Beginners)

4. Lights can heat up the aquarium

Another factor that is usually overlooked when it comes to lighting for aquarium is that some types of light not only produce light but they can also produce heat. And can warm up the water in your aquarium.

The types of light that can heat up the water in your aquarium are as follows:

  • Incandescent
  • Metal halide
  • VH fluorescent

Usually, in large aquariums, high temperature due to aquarium light is not an issue because as the aquarium contains a lot of water the heat gets distributed.

However, these lights can heat up the water in smaller tanks very rapidly.

They can heat up the water in a smaller tank so much so that it can kill the fish and live aquarium plants in the tank.

Ideally, it is best to avoid these lights in your aquarium and use LED lights instead.

There are several benefits of using LED lights over other types of aquarium lights

  • First of all, they produce very little heat if not any
  • They consume less electricity compared to other types of aquarium lights
  • And there is a wide variety of colors available in LED aquarium lights

You can check out my recommended like here

Do Aquarium Plants Need Light? (Do they really need a special light)

Consistency is important

planted fish tank with aquarium light on

Feature image – Author: Eric Gillingham Licensed by CC BY 2.0 Cropped and resized

First of all, you’ll need to be consistent with the light to figure out how many hours of light you should provide to your aquarium.

It is kinda a trial and error process.  

Basically, you’ll need to provide specific hours of daylight every day for at least a few days

Then after a few days, if you noticed algae growth then you should reduce the amount of light you provide to in your tank.

On the other hand, if you don’t see any algae then you should increase the light by about one more hour every day.

Even after you figured out the hours of light you should keep on in your aquarium, you need to be consistent with the lighting. Or else algae can grow in your aquarium pretty quickly.

The best way to be consistent with the lighting

So the best, cheap, and convenient way to provide light consistently in your aquarium is to use a timer.

The timer will automatically turn on and off the light at the same time ever day.

You can find a timer at a very cheap price and it can literally save your life.

Because once the algae start growing in your tank, it can take several days to remove it completely.

So I highly recommend you to get a timer for your aquarium.

I recommend Nearpow timer. You can check it out at Amazon here.

As you can see it is very cheap.

This timer also comes in handy when you are on vacation.

You just have to set the timings into it and it will automatically turn on and off the light for the week.

20 Tips to Maintain a Healthy Aquarium

FAQ

faq image with fish tank and aquarium light

Can I leave my aquarium light on 24/7?

You should never keep your aquarium lights on for 24/7.

There are are several reasons you should not do so but the most important is it will cause algae growth in your tank.

And you can spend literally weeks if not months to clean out algae from your aquarium.

Besides, just as we do fish also require darkness to sleep. So keeping lights on 24/7 can affect their health negatively.

Also, for the healthy growth of your fish and live aquarium plants, it is always a good idea to mimic their natural habitat i.e. the day-night cycle they experience in nature.

Do Aquarium Plants Reduce Algae? (5 Best plants to reduce algae)

Should I leave my aquarium light on while on vacation?

You should not keep your aquarium lights on when you are on vacation.

A convenient way to automate the lighting is to use a timer.

I recommend Nearpow timer. You can check it out at Amazon here.

As you can see it is very cheap. And it has a functionality that allows you to set the time at once for the whole week.

So once you set the timings it will turn on and off the lights at the same time automatically every day for the week.

15 Things You Must Know Before Buying Your First Aquarium

Is blue light good for fish at night?

If you have Nocturnal fish in your aquarium then blue light can help them see and forage in the aquarium at night.

It will also allow you to see their activity.

However, you can’t keep the blue lights on throughout the night. Because it can cause algae growth.

You can keep turn on the blue light, one or two hours before shutting down the light completely.

If you don’t have any nocturnal fish in your aquarium then there is no point keeping the blue light on during the night.

6 Best Aquarium Plants to Prevent Algae (Detailed information)

Can fish tank light be too bright?

Fish tank light can be too bright. You can know when you’re fish tank light is too bright if you notice algae growth in your aquarium.

In this case, you should reduce the hours of light you provide in your fish tank.

Or if your fish tank light has the functionality to reduce the intensity of light then you should do it.

Most of the fish will not bother about too much light. 

However, if you notice your fish start running here and there trying to find a place to hide behind as soon as you turn on the light then it is a sign that you’re providing too bright light in your fish tank.

However, fish can get used to this quite quickly.

Another thing you can do is, you can increase the light gradually if your aquarium light has that functionality.

Besides, there are some aquarium lights that have the functionality to mimic the sunrise and sunset. So in these lights, as the light increases gradually the fish will not get shocked by sudden bright light.

15 Mistakes Beginners Make with their Goldfish Tank (How to avoid them)

Can fish sleep with the light on?

Just as we do, fish also requires darkness to sleep. So fish can’t sleep with the lights on.

If you keep the lights on during the night then, as fish will not get enough sleep, it’ll cause stress in them.

If they don’t get sleep for a long time then this can also lead to death.

Besides, algae will grow pretty quickly in your tank if you keep lights on at night.

How Long Do Goldfish Sleep? (What to do if it’s sleeping a lot)

Conclusion

Overall, you should not keep your aquarium lights on at night.

Keeping aquarium lights on during the night can affect fish negatively. And it will also cause algae growth in your aquarium.

You should keep lights on anywhere between 8 to 12 hours every day depending on your setup.

I hope you found this article helpful.

If you do, please share it.

Happy fishkeeping!

Sharing is caring!

Leave a Comment