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Should I Turn My Fish Tank Light off at Night

People may have various questions when they keep a fish, one of the most common questions is should they turn the aquarium light off at night. The answer is yes, you should turn off the fish tank light at night.

Like human beings, fish need darkness to rest at night. But unlike human beings, most of them do not have eyelids, that is why you see fish sleeping with their eyes opened.

The light can make their color brighter but if you keep the light on all the time, your fish will not sleep and their health will be affected.


Why do you need an aquarium light

Now you have known that you should turn off the light because fish need darkness to rest, but why do you need an aquarium light during the day, isn’t daylight enough?

Aquarium light is not just for illuminating. It can not only provide the energy and oxygen your fish and plants need but also stimulate the growth of photosynthetic plants and organisms.

In addition, it can make your fish tank more ornamental and make the colors of your fish more vivid.


The bad effects of an aquarium light at night

Speed up algae growth

If you keep your aquarium light on for a long time, the algae in your aquarium will grow quickly. We know that algae are important for aquatic life, but excessive algae will bring about a lot of trouble.

The most obvious one is your aquarium will look dirty, which affects the aesthetics of your fish tank. Another problem is that cleaning the algae is a nightmare. It will cover the plants, decorations and glass in your aquarium, which makes it even harder to clean your aquarium and very time-consuming.

algae in the tank

Influence plant growth

Aquarium plants need light to grow since photosynthesis can only occur in the presence of light. However, you can see plants in nature are exposed to light for about 12 hours and darkness for about 12 hours. This is the law of nature and the law of plants growth. Plants also need break time, excessive light will stunt their growth rather than promote it.


Influence fish health

A good rest is important for fish health, just like sleeping well is essential for human beings. If not sleep well, fish will feel lethargy and lose their appetite. With time passing by, those fish will get ill or even die.

Fish are sensitive creatures, being exposed to light for a long time will make them feel stressed and become aggressive. They will attack their tank mates and at least one of them will get hurt.


How long should an aquarium light be on

You are suggested to keep the light on for about 12 hours and keep it off for about 12 hours as well. But it is only a suggestion because you should consider many factors when determining how long should you keep your aquarium light on.


Live plants

live plants

Whether you have live plants in your aquarium matters a lot when determining the number of hours you should keep your aquarium light on. If there are live plants in your aquarium, you need to keep your light on for about 12 hours because they need the light for photosynthesis. But if you don’t have any live plants, you need to shorten the time to about 8 hours.

In addition, the types of live plants will influence the number of hours you should keep your aquarium light on. In a cold environment, you should keep plants that can adapt to the cold temperature. With those live plants, you just need to turn on the light for about 8 hours. But if your plants are suitable for a warm environment, you need to prolong the time to about 12 hours.

If you’re not sure about the specific time, you can start with 10 hours. Keep your aquarium light on for about 10 hours, then observe the growth of algae. If there are no algae in your fish tank, you can prolong the time, if there are many algae, shorten the time.


Fish types

You may notice that the type of fish you keep is an important factor in fish-keeping. It will influence the selection of the tank size, filtration system, heater and so on. In this article, it affects the number of hours you should keep your light on.

For fish like Tetras and Cichlids that prefer to live in a dark environment, you do not need to let them expose to light for a long time. A general rule is, if the fish you keep are tropical fish that enjoy living in a light environment, give them about 12 hours of light. If you are keeping some fish that like a cold environment, 10-12 hours of light is enough.

There is a tip for you if you can not adjust the time for some reason, you can add some live plants or other decorations in your fish tank to provide some shade for your fish to hide.


The position of your tank

It is also a vital element. If your tank is placed in a room where there is plenty of light, 12-hour lighting is not needed, you can just keep the light on for 8-10 hours. Otherwise, if your tank is placed in a dark area, you need to turn on the light for a longer time.


How to regulate the lighting

Set a timer


[Know more]

A timer is a device that can automatically turn lights on or off according to your settings. For example, if you set the timer to turn on at 7:00 am and turn it off at 6:00 pm, the timer will do as you set.

You may forget to turn off the light because of working too late or other reasons, you may need to go for a journey or you are on a business trip so you are not able to control the light. A timer would take care of your worries.

If you don’t want to set too much equipment in your tank, you can choose a light with an inbuilt timer. There are many different kinds of lights on sale.


Add moonlight


One important role of an aquarium light is it helps you keep an eye on your fish and notice their irregular behaviors in time. Once you turn off the light, you can not see what happens to your fish, so you can consider adding moonlight to your fish tank.

Unlike ordinary light, moonlight will not speed up the growth of algae in your fish tank and it will not affect the health and growth of your fish and other plants.

In addition, in nature, when the sun goes down, the moon comes out with moonlight, which produces a brightness of low intensity. Wild fish are living in such an environment, so adding moonlight to your fish tank is a kind of imitating, imitating the natural light.



Should I turn my fish tank light off at night? I believe you have got the answer.

Fish are similar to human beings to some extent, they need light and rest, they are sensitive to water temperature, some of them need tank mates, they do not like noise and they will get stressed when the environment changes.

If you take good care of them, you will find much joy. They will not only accompany you but also make you full of happiness.


Related topics:
How to Get Rid of Algae in Fish Tank?
Do You Need a Light in Your Fish Tank?

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