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Why Do Fish Go To The Top Of The Tank? 4 Main Reasons

Why do fish go to the top of the tank? The most common reason for such behavior is the lack of oxygen in the water. Fish need a sufficient amount of oxygen, which they consume from the water. If the water is contaminated with more carbon particles and less oxygen, the fish may have trouble breathing underwater. Fish seek oxygen from the air. Therefore they swim to the top of the tank to get fresh air.

Why Do Fish Go To The Top Of The Tank

Another reason is the high-stress level causes the fish to stay near the surface. Find what is causing them to stress in the water. It can be unclean water, filtration problems, less oxygen, food, or illness.

What should I do if my fish are gasping?

The water surface is oxygenated. Fish require oxygen to breathe on the surface water. If the oxygen level decreases in the water, the fish might not choose to reach the surface for the oxygen.

They rise to the top of the tank and gasp. Several other factors may cause fish to gasp at the surface. You should check the behavior of the fish to know the condition better.

Why are my fish swimming at the top of the tank?

Lack of oxygen in the water, high-stress levels, and illness are reasons why fish swim to the top of the tank. Check the condition in your aquarium to understand what causes them to stay on the top of the tank.

What should I do if my fish are gasping? How to fix it?

There are several reasons why your fish is having a gasping problem. Checking the following states of the water would help you to fix the issue.


The low oxygen level in the water would cause the fish to move to the surface. They seek oxygen at the top of the water tank, where the oxygen level is high. Clean the water and run the hose to pump the air in the water. The filtration process also performs the same task and improves the water quality.

Oxygen is essential for the fish, and you should keep track of it.

2. Temperature:

The water temperature should be moderated to keep the fish in perfect health condition. The warmer water gets less oxygen and reduces the breathing capacity of the fish. If the atmospheric temperature rises in the tropical region, the aquarium temperature also will go up, causing the water to heat up. Keep the temperature in average condition.

3. Water Quality:

Reduced water quality causes the water to get contaminated with ammonia and nitrite substance. The test of the water changes where fish finds it hard to breathe. You should regularly perform the 50% water change procedure to keep the water breathable. Top up with de-chlorinated top water.

4. Disease Infection:

Various types of diseases affect the health of the fish. Check for infection on the skin of the fish. Some types of spots clamped fins, and secondary infections such as fungus could cause the fish to gasp on the surface of the water. The disease attacks the tissues of the fish, making them ill. Consult the expert to find the reason for the illness.

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Can gasping for air stress the fish?

Yes. There are possibilities that after some time, the fish may develop stress and they fall sick. The gasping for the air is not the natural behavior of the fish. You should check the water condition and other aspects such as disease affected on the fish.

Can gasping affect the growth of fish?

Yes. Gasping indicates that the fish is not receiving the required oxygen for breathing. It will affect their overall health and reduce their growth level and reproductive ability. You should check the water condition to fix the problem.

Fish that are supposed to breathe at the top of their tank

Some breeds of fish look for oxygen at the top of the fish tank. It is their normal behavior to swim at the top and consume oxygen. It would be best if you did not mistake the lack of oxygen issue. This is a normal condition for those fish who like to stay at the top.

For example, the betas and gourami reach the surface to breathe the air. If you have some of these fish in your aquarium, then know that it is normal for them.

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Do fish swim at the top of the tank at night?

Not always. Fish does come to the top of the tank at night when they find it difficult to breathe underwater. In normal conditions, you will not see such behavior. You can turn on the hose and see if the fish stays underwater all the time.

If they usually behave when the filter is turned on, it indicates the fish need more oxygen to breathe. They will swim to the top only when there is less oxygen.

How do you know if your fish is struggling to breathe?

If your fish stays most of the time at the surface of the water, it is a sign of less oxygen in the water. At the top of the water, the oxygen level is high compared to the water’s bottom. It would be best if you tracked the behavior of the fish to understand what is causing them to struggle.

Fish will stay in one place without moving in the water. It will seek a place where they can find a sufficient amount of oxygen, such as near the hose, top of the water tank, etc. Fish will stop eating. Such behavior is a clear indication that the fish is stressed and are struggling to breathe.

Fish gasping for air after a water change?

When the large unit of water is suddenly changed in the tank, the water reacts to the exiting fish waste, uneaten food particles, and deal leaves, and plants. It creates a chemical reaction in the water, which makes the water un-breathable. Fish cannot tolerate such drastic change causing them to gasp for the fresh air. In the worst-case, fish die when water is changed.

Therefore, you should change the water in the small unit daily to avoid a drastic change in the water condition.

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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.