What Does Blue Light in Fish Tank Do

What Does Blue Light in Fish Tank Do?

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Lighting is vital for a fish tank. Not just for aesthetics either. It also plays a role in the health of your fish. There is no lighting more important than that of the blue light. In fact, if you buy just one type of lighting for your fish tank, you need to make it blue.

So, what does blue light in a fish tank too? Well, blue light is meant to signal the transition between night and day for the fish. Without clever use of lighting, your fish wouldn’t know when the night rolls in. This means that they would never sleep. This will result in animals that are far too stressed out. 

Our experts do want to go into this in a little bit more depth on this. We even want to talk a little bit about when you should be switching that blue light on and, perhaps more importantly when it should be switched off again. Hopefully, by the end of this page, you will know everything that you need to know about blue lights in a fish tank.

What Does Blue Light in Fish Tank Do?

Lighting serves a variety of different purposes in a fish tank. In many cases, the lighting is going to be purely aesthetic. However, for a few hours per day, blue lighting is vital for the health of your fish. It helps to ensure that that their behavior is in line with how they would act if they were out swimming in the wild. Blue lighting is, honestly, the most important lighting that you can get for your tank. 

Now, chances are that you already have main tank lighting. This is likely going to be some sort of white lighting that will allow you to watch your fish during the daylight hours. This is fantastic. However, it is not a type of light that you are going to be able to leave on all day.

In the wild, the light in the water will over the day-to-day life of a fish. For example, some fish will know that when it starts to transition into the nighttime, that is when they should go and hunt a little bit of food. For other fish, the movement into nighttime is when the fish will start to hide away from all of those hungry predators.

Just because your fish were born into captivity doesn’t mean that they have lost these natural instincts. The fish still need to know when it is night and day. This is the main reason for having blue lighting in a tank. Let us explain.

Signal the Transition Between Night and Day

Many people turn the blue light in the aquarium on for just a couple of hours per day. The blue light is meant to simulate moonlight. So, you switch the main tank lights off (this is the sunlight), the moonlight comes out (the blue light), and then all the lights go off (the night).

If you could look into a shadow body of water when the moon comes out, you would notice that fish start to get into their nighttime routine. This may mean that they hunt a little bit of food, or it may mean that they hide away. This is because the fish instinctively know that the night is about to come, and that water is going to get exceedingly dark.

Basically, the blue light helps to bring out the natural nighttime behaviors for your fish.

Help Plant Growth

There is evidence that blue light helps to increase the growth of plants in your tank. Many aquarium owners have discovered that having a blue light switched on for a couple of hours per day in the tank results in faster-growing, healthier plants. This means that if your fish tank relies heavily on plant life, then having blue light is going to be fantastic for you.

The blue light is also going to benefit the plants in the tank in exactly the same way that it benefits the fish too. Plants can’t be constantly exposed to daylight. It is stressful for them. The blue light will also help to signal the transition between light and day for your plants. Again, this is going to help them to grow a whole lot healthier.

Now, there are some people that claim blue light helps to slow algae growth down. It doesn’t. Blue light is going to speed up algae growth. Algae is a plant, after all. This means that you will probably need to stay on top of your tank cleaning regime.

Calm the Fish Down

What you must remember is that most fish are in a constant state of alert. Fish never know when they are about to be a snack for a much larger fish. This means that during the day, they will be constantly alert. Many of these fish know that they can’t relax until the nighttime comes.

Blue light is known for helping fish to relax in the tank. If you gradually turn on that blue light of an evening, you will notice that your fish start to calm down. They may even try and find somewhere that they can sleep.

If you had the main tank lights on at all times, the fish will never be able to relax. In their minds, it is still daylight. It means that they are still at risk of being gobbled up by a predator. 

Thanks without blue light often result in the fish becoming sick, stressed out, and, ultimately, dying a whole lot earlier. It is not going to be a pleasant experience for your fish in the slightest. Imagine if somebody messed up your sleep schedule!

Do You Need a Blue Light in the Fish Tank?

In most cases, yes.

There are some people that will have the aquarium close to a window so that the natural light flowing in will give the fish a good indicator as to whether it is light or dark outside. However, we don’t like this method. If the aquarium is too close to a window, then it could result in the water temperature becoming a bit unstable, particularly if it is hot outside.

Other than this, you should always have a blue light in the fish tank. it is the only way the fish is going to know when it should be awake and when it should be sleeping.

When Should You Turn the Blue Light in the Fish Tank On?

There are actually two answers to this question, and it is going to be dependent on the type of fish that you have.

Nocturnal Fish

If you have nocturnal fish, then you should turn the blue light on at night.

You should then leave the blue light on all night. This will encourage the nocturnal fish to come out and swim around.

You should not do this if there are any fish inside of that tank that are not nocturnal. This will agitate them.

All Other Fish

For all other fish, we recommend that you split the day up into 2 x 12-hour parts. One 12-hour period for the night, and the other for the day.

In the 12-hours of the daytime, you do not want that blue light on at all. It will agitate the fish as they will never be receiving that signal telling them “it is time to sleep now”

For the nighttime, you want to have the blue lights on for the first 2-hours. Then, they get switched off. However, try to make sure that you do not turn them straight on at high intensity, and then suddenly off. This will make the fish a bit suspicious of what is going on. Instead, use a dimmer switch to gradually turn up that light and, as the 2-hours move on, gradually turn down that blue lighting.

For the rest of the nighttime, the lights should be completely off. This includes the main tank lights.

Related Questions

Do You Have to Use a Blue Light in an Aquarium or Can You Use a Different Color?

You should only be using a blue light. If you use any other color, then it may irritate the fish, or at least make them feel a little bit uncomfortable. While you can use other colors of lights to decorate the outside of the aquarium, you should only ever have blue inside of the aquarium.

Are LED lights better than other aquarium lights?

Yes. They tend to consume a lot less power than normal aquarium lights. They also tend to last a lot longer. In fact, chances are that you will never have to replace LED lights in your aquarium. They last for thousands of hours. LED lights often have better features on them too e.g. the ability to change how bright they are.

Can You Use a Timer to Turn on the Blue Aquarium Lights?

Absolutely, and it may make sense to use one. It will help to ensure that the lights are being turned on at the right time every single day. It also ensures that they are switched off exactly when they need to be switched off.

See Also:
Can You Put Decorative Sand in a Fish Tank?
Can You Use Reptile Decor in a Fish Tank?
How Long Does Fish Tank Sealant Last?
How Long Does a Fish Tank Filter Last?