Should You Turn Off the Lights of Your Fish Tank at Night?

Updated on by Patrice Alsteen | Affiliate links may be present.

Lights in your fish tank provide you the ability to see your fish and plants, but are they necessary, especially at night?

Fishes need about 12 hours of light a day. They require darkness to sleep, and you should make sure to turn off the light in your fish tank at night.

Effects of Too Much Light

Besides providing darkness for your fish to sleep, there are a few other reasons why you should turn your aquariums lights off.

Causes Stress

Leaving your lights in your fish tank on for long periods of time can cause your fish to stress. You want to provide your fish with the most natural habitat possible, and you should try to imitate the day and night cycle daily.

If you deny your fish a night cycle, it can cause appetite loss, persistent fighting, and lack of sleep which can stress your fish out. These symptoms often lead to death, if prolonged.


Leaving the light on in your fish tank can cause the rapid growth of algae. Algae is not just hideous to look at but can overrun your tank and steal all the nutrients meant for your aquarium’s plants and fish, eventually killing them.

If you see that Algae is forming quickly in your aquarium, you should limit the amount of time you keep your light on.

How Long Should You Leave Your Light On in Your Fish Tank?

Light is important in the health and growth of your fish and plants. If you have a new tank, try leaving your lights on for 8-10 hours per day.

This is a general rule and if you see that no algae is forming after a few weeks, increase the duration of light by an hour every few weeks until you are up to 12 hours a day.

Should algae start to grow, you can decrease the number of hours of light per day. If this does not work, there is a possibility that your light is too bright, and you should opt for something less intense.

The Benefits of a Light in Your Fish Tank

Light illuminates your tank and makes it more aesthetically pleasing for your viewing pleasure, but it also provides energy and oxygen, which aids in the well-being and growth of your fish.

Most people have their fish tanks in a space where they acquire natural light, but you must have lights in your tank if yours is in a darker room. Light also provides plants with the elements they need for photosynthesis.

Types of Light for Your Fish Tank

Acquiring the proper lighting for your fish tank is vital. There are different types of lighting to choose from for your specific needs.

LED Lights

LED lights tend to be the most popular option for aquariums. They offer a slimmer design, different colors, and temperature controls.

LEDs are cost effective and easy to maintain. They come in a wide variety of shapes and sizes. LEDs are also notorious for generating consistent coloring throughout their operational lifetime.

Fluorescent Lighting

Fluorescent lighting is the most bought lighting for fish tanks, mainly due to its low price. They come in numerous sizes that can fit any fish tank, making them appealing to consumers.

However, due to the bulbs being circular tubes, they are unsuitable because a large portion of the light reflects upwards, avoiding the fish tank.

T-5HO Fluorescent Lighting

T-5HO fluorescent lighting is a premium form of fluorescent lighting.

Their bulbs are much brighter than the standard bulbs. These lights would work well in a larger aquarium that requires a brighter, more profound effect.

However, these bulbs produce much more heat, leading to a build-up of Algae, so it is essential not to use them in smaller tanks.

Metal Halides

Metal Halides bulbs are the epitome of lighting for fish tanks. They are renowned for their capability to imitate the effects of natural light underwater. Light exudes from a single point on the unit, so if you have a larger tank, you might need a few bulbs.

Due to all the unique fixtures they require, they are the most expensive option for your aquarium.

Using a Timer for Your Fish Tank Lighting

Using a timer like this can save you a lot of time and worry. Once you understand how much lighting you need for a balanced environment in your tank, you should incorporate a timer. They are cost-effective and will allow you to control the lighting in your tank accurately.

Final Thoughts

To maintain the optimum health of your fish and plants, you should always put the lights in their tank off at night.

Fast-growing algae is the first sign that something is wrong in your tank. It might be the amount of time you leave the lights on or the warmth and brightness of your lighting. Always ensure you are using the correct lighting for your type of aquarium.

About Patrice Alsteen

Patrice has been an animal lover, right from her childhood. She's currently enjoying the company of her cat, dog, aquarium fishes, and a few small furry companions.

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