How Many Hours of Light Do Aquarium Need? (Explained)

So you have purchased your aquarium. You are pretty excited about it. You are making plans to make it look great. You are reading tons of articles and blogs each day to ensure that you do everything.

Suddenly your gaze is stuck on one topic and, i.e., “How many hours of light does the aquarium need”? 

The answer to this question can look simple, but it is not. Every live plant and fish species reacts to light differently. Most of the articles will tell you that 10-12 hours of light is enough for a day.

But it depends. For example, a plant named “Glossostigma Elatinoides” needs very high-intensity light to grow. Other species won’t require light intensity, but this plant does.

Today, we are going to discuss the light requirements for the aquarium. We should consider many factors before deciding the right amount of time. It can differ for different new species.

Let’s start. It’s time to illuminate aquatic life. 

Why is light necessary for an aquarium?

1. For Fish

Light is vital for your aquarium. Without light, plant life inside your aquarium will suffer. Light is crucial for your fish as well. 

Species like goldfish require light. Without the ample amount of light, it will just fade away. Each freshwater fish has different needs for light intensity. 

Bottom dwellers’ fishes, such as catfish and plecos, don’t need that much light. They are accustomed to low light levels inside water. Fish in the tropical region will always enjoy more sunshine than their subtropic counterpart.

Light On Fish Tank

For tropic water fishes, you should supply them with 12 hours of light inside the aquarium.

You can supply them with 8 hours of light for cold-water fish. However, if you have enough hiding spots for them, you can go for 12 hours of light.

For top and medium dweller fishes, you can provide 10 to 12 hours of light each day.

In the case of bottom dwellers, even 8 hours of light is enough. They can live without high-intensity light.

Wrong light brightness can trigger stress inside the fish, and it can cause death.

2. For Plants

 For us, lighting inside the aquarium is only for viewing purposes. However, for plants, it is different. Plants are heavily dependent upon the diurnal light pattern. So a good amount of light is paramount for them.

Each plant species have a different need for light. Some plant species such as Java Moss, Anubias, and Java fern will require only 8 to 10 hours of light per day.

Light on Planted Tank

But, some light-hungry plants need 12 hours of light, CO2 addition, and fertilizer dosing. If you are a beginner, you should always consider needed low light plants.

You should keep in mind that your fish types should match with plants type. Always pair tropical plants with tropical fish and vice versa.

Factors on which aquarium light intensity depends

There are many factors on which your aquarium light intensity depends. We need to understand all of these factors to deduce the correct answer for our situation. 

Let’s have a look at these factors.

1. Amount of fishes in the aquarium

If your fish tank is heavily populated(85% filled), you can leave your light on and off for 12 hours cycle. Generally, in communal tanks, this phenomenon occurs.

By doing this, you are setting the fish’s circadian rhythm. This will help fish know when to sleep, when to be active and when to eat. It will be beneficial for the fish.

If you have nocturnal fish, then the absence of light will tell it to go and scavenge the food in the tank.

2. Types of fish species in the aquarium

There are different fish types. Some notable types are tropical fish, subtropical fish, top dweller, medium dweller, and bottom dweller fish. 

All of these fishes have slightly different requirements compared to each other. However, they are not poles apart. But the lighting duration can vary 2 to 3 hours at max.

3. Amount of plants inside aquarium

Aquatic plants need three things to grow, i.e., Sufficient light, correct temperature, and in some cases, CO2. Just like fishes, certain plants have different light needs.

CO2 Tank

Tropical plants will need 12 hours of light. That’s why it is always recommended that beginners get low-life plants. 

4. Are there any critters inside the tank?

Invertebrates such as shrimp, crayfish, snails, etc., don’t need high-intensity light. Unlike their tropical counterpart, they can easily survive in low-intensity light.

But, if high-intensity light is present, you should provide them with enough hiding spots.

5. Is Algae causing problems inside your tank?

Algae can be your friend or foe. It depends on your situation. If your tank houses algae eaters like siamese algae eater, shrimp, snail, etc., the algae can help life thrive inside the tank.

In that case, provide high light intensity as more light is proportional to more algae.

However, if your fishes do not like algae, more algae can create problems. You need to make sure that the algae level is within the range. Don’t provide high-intensity light for long hours to your tank.

6. How much natural light is the aquarium getting?

If your fish tank is already getting ample sunlight, there is no need to provide longer-duration light. If you provide extra light with sunlight, then it can create problems.

It is always recommended that you not depend upon sunlight for your tank. This can make your water unstable, promote algae bloom and increase the stress level in the fish.

What if you give too much light or too little?

If your aquarium does not have the right light, it will become unstable. An unstable aquarium can be dangerous for your plants and fish.

An algae boom will happen in an imbalanced environment, and its growth can be tremendous. This will be very dangerous for your fish’s life as certain fishes hate algae.

Due to the excessive amount of algae, your fish will start acting strangely. It will come under stress. Due to this, they will start dying if not intervened.

Too much light can also cause stress in your fish. This will create a problem for you again. 

For plants, the situation will also be not easy. Too much light will cause unexpected growth of the plant. It will disturb the tank harmony. Algaes will start consuming all the nutrients, and your plant will not get enough nutrients.

In low light, your plants won’t be able to grow. This will cause your plants to die.

Difference between Led and fluorescent light?

LED lights have become famous for aquarium tanks for the past couple of years. They are slowly displacing halogen(fluorescent) light from their top position. 

Although fluorescent light is cheaper than LED light, there is a twist. Once installed, a LED light can efficiently work for 5-6 years. But halogen light needs to be replaced in a year. As with time, it loses its brightness.

So more and more people are getting LED lights in place of halogen.

How to regulate aquarium light?

There are two ways with which we can regulate aquarium lights. The first one is the manual method. As the name suggests, we can control light intensity. We can quickly turn it off and on according to the schedule.

The second way is to use an automated timer. The timer is programmed to turn the light on and off according to the time. You can set the light timer easily according to your wish.


We have seen the different factors on which aquarium lighting depends. It varies according to plants and fish species.

For certain species, less light is necessary, and for species, a high amount of light is needed.

If you talk about the average time needed for an aquarium, the answer will be 10 to 12 hours. But, we recommend you research before selecting the right amount of time required for lights.

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