How To Get More Oxygen in Your Fish Tank

Oxygen is one of the essential elements of any living organism, even for fish, and Aquarium water should have stable oxygen levels.

Most of the time, new aquarists or beginner aquarists tend to forget the importance of oxygen in the water, and I also made this mistake when I was a beginner.

There is a reason why we tend to forget about oxygen because we can’t see the oxygen levels with bare eyes.

A low oxygen level of water is dangerous for any fish, and they will suffocate to death. And high levels of oxygen can lead to many health issues.

How to get more oxygen in your fish tank?

There are many ways to do that. You can increase the surface area of the aquarium, and you can also add an air pump to your aquarium.

Before you add an air pump or any other measures to lower oxygen in your aquarium, you should read this article thoroughly to understand more about the oxygen-related issue in your aquarium.

This article will learn How to get more oxygen in your fish tank, know if your tank has a low oxygen level, and many more.

How to know if your tank has a low oxygen level?

Identifying a low oxygen level in your aquarium is difficult without using any test kit. Still, there are ways to determine the low oxygen level in the water.

When the oxygen level goes down, you will notice some change in your aquarium fish, and it would be best to observe your fish regularly.

If you notice any behavior mentioned below, test the water immediately to check the low oxygen level.

There are many signs of low oxygen in aquariums. Let’s see what are sings you should look for.

Difficulties in breathing

Like other animals, fish also need to breathe oxygen. When aquarium water has less oxygen level, the fish will have a breathing problem.

You will notice rapid gill movement of the fishes in your aquarium, which is a strong sign of a low oxygen level in an aquarium.

Gasping on the surface

Sometimes gasping on the surface is difficult to understand as normal or something else. Why this confusion, you may ask.

Many fishes come to the surface to gasp with a wide-open mouth, fish like Betta. But all of your aquarium fish display this behavior, and there is certainly low oxygen in your aquarium.

Lake of appetite

A low amount of oxygen in water can also cause a lake of appetite in your fish. You will notice the fish are not eating as much as they should be.

Sluggish fish movement

When animals run and play, they need oxygen to fuel themselves, and fish also need oxygen to play and run. But if your aquarium oxygen level is lower, they will tend to move slowly, and you can see their playful nature.

But sometimes they take rest or even sleep. If you observe them, you can identify the difference between resting and sluggish movement.

How the oxygen dissolves in a tank?

There are three ways oxygen gets dissolved in water:

  • Diffusion from the surrounding air.
  • Through aeration.
  • Photosynthesis process by plants.

A gas exchange continuously occurs on the water surface with the surrounding air called diffusion. The carbon dioxide is released from the aquarium water and enters the atmosphere. The same happens to oxygen, and oxygen enters the water from the air.

Diffusion is a natural process, and you can boost this process using manual or mechanical water movement.

Live plants are a great source of oxygen in aquariums. Photosynthesis uses light and carbon dioxide to produce plant food and produce oxygen that remains in the water.

How much oxygen does a fish require?

There is no direct answer to this question. The safe level of oxygen varies according to fish species. The 4-5 mg/L dissolved oxygen is good for aquarium, and the best level is 6-8 mg/L.

Do not go below 3mg/L oxygen dissolve level. Then your fish may die. Even the hardiest fish will suffocate.

Dissolved Oxygen Level (in mg/L)

Below 3 mg/LVery little life.
Above 4-5 mg/LA large variety of life.
6-8 mg/LA healthy aquarium

Low-level oxygen is harmful to fish, but a high oxygen level is detrimental to fish. Water has a little, how much oxygen water can hold.

If the water gets saturated, oxygen can not dissolve in the water anymore. Fish can live happily in this saturated water.

But when the water gets supersaturated, this causes gas bubble disease. Water doesn’t get supersaturated every day, it happens, but it does happen.

What is the cause of the low oxygen levels?

There are many reasons for low oxygen levels. We will discuss four reasons below:


Overstocking is one of the biggest mistakes beginner aquarists can make. If you have a relatively small tank, try to reconsider how many fish you can keep in the tank.

Too many fish will need more oxygen, there will be an oxygen shortage. Try not to make the overstocking mistake.

Water Temperature

There is a direct relationship between water temperature and dissolved oxygen in the water.

Coldwater can hold much more oxygen than warm water. As the water temperature increases, the ability to carry oxygen reduces.

Too high water temperature means low oxygen in the water.

Planted tank with low lighting

Live plants have many benefits to an aquarium. They provide shelter, hiding places even oxygen. However, plants also need oxygen at night.

If you have planted an aquarium with poor quality of light, this may cause your low oxygen in the water.

Algae also work the same way as live plants work. So, you should buy a proper light for your aquarium.

Low water movement

If your tank water doesn’t have any water movement, this can cause low oxygen in your aquarium.

Oxygen is usually rich near the surface of the water, but if there is no water movement, how oxygen will go to the bottom.

The water movement will help to distribute the oxygen in the entire aquarium water volume.

How to increase oxygen in fish tank without pump?

How to get more oxygen in your fish tank naturally? This is what many of you are asking. Now let’s see;

Frequent Water change (40-50%)

A frequent water change will replenish the oxygen in your aquarium.

Pour water from a height.

You can pour the water from some height. The more the height, the more oxygen will get dissolved during the process. Take some existing water from the aquarium, pour it down, and repeat the process several times.

You can also do this while you change the water. Before doing this, place a plate or bowl on the gravel. This will prevent stirring.

How to get more oxygen in your fish tank? (Permanently)

How to put oxygen in water for fish? We will discuss five possible ways how to get more oxygen in your fish tank:


You should follow the guidelines of the fish you want to keep. Every fish has their space recommendation. Learn more about the fish you want to keep.

Overstocking is a bad thing for every aspect of an aquarium. You should avoid this mistake.

The water temperature

You should check the water temperature regularly. There are many reasons for high temperature:

  • Heater malfunction.
  • Light heated the water.
  • The aquarium is exposed to direct sunlight.
  • Very high ambient temperature. (Likely in summer)

Nowadays, heater malfunction rarely happens. Still, this malfunction has happened many times in the past. We should avoid this circumstance in any situation.

You can use a temperature controller alongside your heater. Some brands provide great features, like High and low alarms.

Fluorescent bulbs metal halides can heat the surface of the aquarium. You can use LEDs instead of fluorescent and halides.

You should place your aquarium in the coolest place of your house. Keep in mind that don’t place your aquarium under direct sunlight.

Keep your aquarium clean.

To provide a healthy environment for your fish, you should keep your aquarium clean and improve water quality. Try to change 20% of the water every week.

Remove every extra lying food from the bottom of the tank. Extra food can cause high ammonia in aquariums.

Make a routine to clean your aquarium. Use a good filter for water filtration.

Surface water movement

Surface water movement is an effective way to provide oxygen in your aquarium. There are several types of equipment you can use:

  • HOB Filter.
  • Spray Bar
  • Air Pump & Bubbler
  • Wavemaker

Benefits from live plants

If you provide quality light for your plant, then the plant can be very helpful in oxygenating the water.

If you want to take benefit from having a live plant, you should use a proper light. And also, check the algae growth.

Don’t keep your aquarium light on all the time.

How to get more oxygen in your fish tank? (Emergency)

If there is an emergency, how to put oxygen in the water for fish. In case of emergency, you can use these methods mentioned below:

Ice Cubs and Fan

Suppose the low oxygen level is because of high temperature. You can change some of your aquarium water add ice to the water to reduce the water temperature.


I hope this guide will help you to solve the problem in your aquarium. If you have further questions or any suggestions you can also comment below.

Hey, I am Shuvradeb Biswas a content writer. Fishkeeping is my hobby. There are many problems I faced during my first fishkeeping. So, I made the blog to help new fishkeepers.

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