How Long Should Aquarium Lights Be On(2021)

How Long Should Aquarium Lights Be On(2021)

Aquarium lights not only provide a beautiful view of the tank but also have a great impact on the life inside the tank.

The circadian rhythms of most fishes are dependent on the lighting.

They need light to wake up and dark to sleep. Aquarium light is necessary for the health of fish. But for some fish keepers, it becomes difficult to maintain ideal light hours in the aquarium.

How long should aquarium lights be on and how can you manage them? In this post, you will get all the answers related to aquarium lighting.

Let’s dive right in:

Overview of Why Light is Needed for Aquarium

It is important to know why light is needed for the aquarium.

Generally, the aquarium has two types of life: fish and plants.

Fish need light for their natural sleep cycle. Light helps you to mimic a natural environment for an aquarium.

Excessive dark mode has many risks for the fishes:

  • First, their color will fade and they become passive.
  • Their immunity to diseases will be reduced. They can prone to many diseases, including stress.
  • Their eating habits will be affected as fish like to eat in light.
  • The natural sleeping cycle will be disturbed.

Besides fishes, plants also need light in the aquarium:

  • Plants need light to make food by photosynthesis.
  • Algae growth will be increased by lightning.

Therefore, light is necessary for aquarium in many aspects both for fish and plants. But you have to keep a check and balance on how long should the aquarium lights be on.

Fish Tank Light: How Long Should it be on

If the excessive light mode prolongs, it can be lethal or stressful for fish.

Ideally, fish needs 10-12 hours of lightening for their normal routine. But it is not a panacea, it depends on a number of factors.

The purpose of providing light to the fish tank is to maintain the health of fish and the growth of plants. Keeping the fish tank is not as easy as pretended.

Just keeping the light on is not enough. It needs to be regulated and altered with the dark mode. Apart from the fact that aquarium lighting is a part of room decor, it is also regular practice to ensure an ideal environment.

Which Factors Govern the Lightening Hours?

Several factors govern how long should the aquarium lights be on the tank. It can be tricky to know exactly how and what factors influence the light need. These factors majorly affect lightning hours.

  • The number of fishes in the tank
  • The species of fishes
  • Plants in the aquarium
  • Growth of algae
  • The ambient light of the room

How Does Light Depend on Fish Species

Each fish has its own nature and wild habitat. Some are tropical and some are cold environment fishes. While providing light to fish, their natural wild habitat determines the hours to be provided. Hours of light vary with the fish species and habitat.

The tropical fish like guppies and bettas live in fresh and saltwater. They need the light of 10-12 hours in the aquarium, like their wild habitat.

Other fish species like cichlids and tetras prefer dim light. In the wild, cichlids live in a dark environment. 7-8 hours of lighting will be enough for cichlids. Too bright or intense light adversely affects the health of cichlids.

Some fishes like goldfish and zebrafish can go with 12 hours of light in a day.

For fishes whose light requirement is not defined exactly, the rule of thumb of 10-12 hours will be good options.

The light requirement also depends on the season. In summers, there is enough sunlight. So, you will need fewer aquarium light hours. But in winters, sunlight is not in sufficient quantity.

Therefore, you will have to increase the hours of aquarium light. Change the duration of lightening with the environment and fish demand.

You should try to maintain an ideal and natural environment for the fishes in the tank. And light is a major factor in determining the ideal environment.

Keep the fish tank light on to enjoy a beautiful view of the aquarium and for the fish to be healthy.

How Plants Affect the Duration of Light

Aquarium plants also play a great role in the lighting of the aquarium. Plants are the natural decor of the aquarium. They act as a source of oxygen and food for fish.

Plants need light to perform photosynthesis of making food. Aquarium plants are also the same as ground plants. If you have aquarium plants, you will need a light of 10 hours. Plants will grow and add oxygen to the tank environment. In addition to sunlight, provide supplemental lightning to fulfill the needs of plants.

If you don’t have plants in the tank, provide the light that the fish needs. At the initial stage of plant growth, it is recommended to provide light for a longer period. So that the plants may grow easily.

Choose the plants according to the fish species. If you have tropical fish, choose tropical plants for the tank. They will need the same amount of light as the fish. Tropical plants like java ferns, Anubias, and Moss balls are good for tropical fish tanks.

While for cold water fishes, plants like Anacharis and Hornwort are the best match. The light requirement of cold water plants varies with the season. These plants are easy to care for and maintain the natural ecosystem of the tank.

How to Control the Timing of Light

Providing light to the fish tank is the first step and controlling its timing is the next step. It is somewhat kind of bother for fish keepers to on and off the lights. Too high and low duration both negatively affect the fish and plants.

If you also don’t have time to on or off the lights or you forget it, you can set the timer with the light. The timer will help you a lot in controlling the light of the fish tank. Fix the timing and the timer will automatically on and off the light. The timer is cheap and easy to maintain.

How Does Ambient Light of Room Affect Fish Tank

Glass walls of the fish tank act as a magnifying glass. It transmits light to the inside of the tank with intensity.

If your tank is placed in a well-lit room with windows where sunlight also has contact, you will need less aquarium tank light.

How long should the aquarium lights be on depends on the ambient light of the room.

Enough ambient light or an approach of sunlight to the room will minimize the need for aquarium lights. If the fish is inactive, it may be the sign they are not getting enough light. Immediately turn on the lights to keep fish healthy.

How Algal Growth Affects the Aquarium Light Need

Algae grow at a greater ratio when exposed to light. If you provide sunlight in addition to aquarium lights, algae will grow extensively. You can use the growth of algae as an indicator of light need.

If the algae are growing at an extensive rate, it means you are providing enough light and vice versa. But your goal is not to keep track of algae.

Some fishes also eat algae as food. So algae must be in sufficient quantity in the tank. But too much algae disturbs the natural environment of the tank. Reduce the hours of light when you see the algal blooms in the tank.

Do Light Heat Up the Tank

Temperature fluctuations are the main cause of death for fish. Either the temperature is high or low, it is lethal for fish. If the fish tank is exposed to light for many hours, it heats up the tank.

Apart from hours, the type of light also plays a role in heating the tank. Incandescent and VHO-fluorescent lights heat the tank water.

These lights are too intense for small tanks or bowls so that it can kill the fish. Regularly monitor the temperature of the tank while using lights.

Comparatively, normal fluorescent lights and LED lights are best for aquarium tanks. They use less light and are better for the growth of plants. You can keep these lights on for a longer period without any threat.

Bottom Line

Aquarium light for 10-12 hours must be on for the tank. Both the fishes and plants need light. It is necessary to maintain the ideal hours of light.

You can keep your fish healthy and active by exposing the tank to proper light hours. Alter the light period with the dark period to mimic the natural environment of the tank.

Light is more than a room decor for fish. Their sleeping and eating habits are dependent on proper light hours. As a fish keeper, it is your responsibility to maintain light hours for fish.


Can You Leave the Aquarium Light on 24/7?

Fishes need aquarium light like their natural habitat. They also need darkness to sleep. You cannot keep the aquarium lights on for more than 12 hours. Extensive light periods negatively affect the health of fish. They can become stressed or overstimulated in a longer light period. Algae grow rapidly in light. So, maintain the light to about 12 hours a day.

Are LED Lights Bad for Fish?

A major concern with the aquarium light is they heat the water tank. Incandescent and fluorescent lights can warm the water resulting in negative effects on fish. But the LED lights are best for the aquarium as they are cheap and don’t heat up the water. You can use aquarium lights of red, blue, and green color depending upon your choice.

Can Fish Sleep with Red Light On?

Fish can sleep with a red light on. The science behind the fact is fish cannot distinguish between red and other colors. So fish can sleep when the red light is on and their sleeping pattern will not be disturbed.

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