Breathe Easy: 7 Tips for Increasing Oxygen in Your Fish Tank

Last Updated on 2023-09-20

If an aquarium is well-maintained and not overstocked, low oxygen levels are not usually an issue. But if you see your fish is at the surface of the water gasping for air, this is a sign that something is wrong, and you should look into it more. We all know too well what happens when there isn’t enough oxygen in our fish tanks. It stresses out your fish and makes them gasp for air, which can be very dangerous if it goes on for a long time. In this article, we’ll talk about the dangers of low oxygen levels in your fish tank and how to fix them.

How Much Oxygen Does a Fish Require?

In our aquarium, carbon dioxide and oxygen are always being exchanged. We need oxygen for the fish we keep, and we need carbon dioxide for the plants we grow in water. Not only that, but there are also other things in the aquarium that affect the balance between these gases.

No one knows exactly how much oxygen from the water a fish needs. Many things, like species, size, temperature, and the amount of physical activity, affect the amount of oxygen in the water. But in general, the average amount of dissolved oxygen that an adult fish uses is 5 parts per million.

When you have an aquarium, it’s important to make sure the animals in it have enough oxygen and keep it that way. There are a lot of ways to do that, like installing an air pump or mechanical filter. Just don’t do too much because too much oxygen is just as dangerous as not enough.

What are the Symptoms Of Not Enough Oxygen In Fish

All types of fish need oxygen from the environment to breathe, just like people do. But in an enclosed space, it is hard to tell if there is enough oxygen for everyone. Here are some signs that your fish needs more oxygen.

1. Fish is Lethargic

When there is less oxygen in the water, fish will move around less at first. They will swim with less energy and even eat less. As the oxygen level in the water continues to drop, the fish will start to breathe harder and move their gills faster as they desperately try to get more oxygen from the water by moving more water into their gills.

2. Gasping Air In The Surface

Fish will start gasping for air at the water’s surface if there’s not enough oxygen in the water. When they swim to the top of the water, it’s because they are trying to breathe more easily. This type of breathing at the surface should not be confused with surface feeding or other strange behaviors that some fish, such as the labyrinth fish, show.

3. Rapid Gill Movement

Rapid gill movement may be an indicator of stress or a specific disease, such as flukes, or Ich. But it also means for sure that it is trying to get more oxygen by letting more water flow through its gill.

4. Stressed Fish

One sign that the fish isn’t getting enough oxygen is that it’s showing signs of stress. This means that they are acting and eating in a strange pattern. Some fish even get darker when they are stressed.

5. Loss of Appetite

If your fish doesn’t want to eat, it could be because it doesn’t have enough oxygen. If a fish doesn’t want to eat, it doesn’t necessarily mean it can’t breathe well. However, less oxygenated water makes the fish feel stressed, which makes it not want to eat.

What Causes Low Oxygen in Fish Tanks

As long as there is a living thing in the fish tank, oxygen will always be used up and will run out over time. There are, however, other things that can also use up the oxygen in your fish tank. Here are a few reasons why there isn’t enough oxygen in your fish tank.

1. Improper Use of Treatment Products

Some medications used to cure fish illnesses or adjust the pH of the water can also reduce the amount of oxygen present. If you must use a chemical in your tank, you can play it safe by increasing the water circulation in the tank throughout the treatment duration to ensure there is always enough oxygen in the water.

2. High Water Temperature

Low oxygen levels in the water can also be caused by the water being too hot. Warmer water has a lower oxygen capacity than colder water. Avoid shocking your fish by using ice cubes in a plastic bag.

3. Overstocked Aquarium

The number one cause of low oxygen levels in an aquarium is having too many fish. The more animals in your aquarium that need oxygen, the more oxygen will be used up. One inch of fish for every gallon of water is a good general guideline for stocking a tank.

4. Excess Waste 

As microbes break down the extra organic matter and fish waste, they can use up the oxygen in an aquarium. Algae that grows in the tank will also consume oxygen and keep underwater plants from getting enough light. The amount of oxygen in the tank will go up if the gravel and walls are cleaned out well.

5. Low Lighting For Plants

Live aquatic plants can sometimes reduce the oxygen levels in an aquarium. Live plants can sometimes use up all the oxygen in an aquarium. Plants take in carbon dioxide and give off oxygen when they are exposed to light. But when it’s dark in the tank, the process goes backwards, and your plants, including algae, will take in oxygen.

6. No Surface Movement

The amount of oxygen in still water is low, so aquarium water needs to be stirred or moved often to keep enough oxygen. When the water in an aquarium is constantly stirred, the oxygen from the surface will be dissolved in the water. It is best to put something in your aquarium that moves the water around all the time.

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Ways to Increase Oxygen In Your Tank In An Emergency

When you get home from work, you might find that the power has been turned off. This means that there is nothing you can put in your aquarium to help dissolve oxygen. Here are a few things you can do to temporarily add oxygen to your tank when something like this happens.

1. Perform a Large Water Change

Doing a 50% water change is another way to raise the amount of oxygen in the aquarium. The freshwater you put in the aquarium has more oxygen, which will help raise the level of oxygen in the tank.

2. Put Airstones in Your Aquarium

An aquarium bubbler is another name for an air stone that sits in your fish tank and mixes air into the water. In this way, it can greatly increase the oxygen in the water. Air stones also help fish deal with water resistance, which can be essential for their growth.

3. Install Battery-Powered Air Pump

Power outages happen often, and even more so if you reside in a place that gets a lot of storms. If the power goes out and you don’t have a generator, any aquarium device you have that needs electricity in your aquarium will also be out. If the power goes out, a battery-powered air pump is a fantastic way to keep the water in your fish tank moving.

4. Use Fans

One way to cool down the warm water in an aquarium is to put fans that blow air right on the water’s surface. Not only does it cool the water, but it also stirs up the surface of the water, which can make your aquarium have more oxygen.

5. Manually Stirring The Water

Stirring the water by hand is another great way to increase the amount of oxygen. This makes the fish tank water move, which increases aeration. Just make sure to wash your hands first and do it slowly and softly so you don’t stress your fish too much.

6. Pour Water From A Height

If there isn’t enough oxygen in an aquarium, you can temporarily fix the problem right away by pouring water into the fish tank from above. The splashes made from falling water into the fish tank increase dissolved oxygen in the water.

7. Reduce The Water Temperature

If the elevated water temperature in your tank is making the oxygen level drop, you can cool the aquarium water by placing some ice cubes in a tightly closed plastic bag and holding that bag in the aquarium.

Ways To Increase Oxygen In The Fish Tank (Permanent Solutions)

The fish and other animals in your fish tank will always need oxygen to live. So it’s smart to find a permanent solution that will help you get more oxygen and keep it there. Here are some ways to get more oxygen into the fish tank.

1. Install a Hang-on-back (HOB) Filter

The most common type of aquarium filter is a HOB filter. They are a good way to add more oxygen to fish tanks, and they are also small and simple to set up. The HOB filter sends out filtered water, which gets mixed with air and spreads out evenly in the fish tank.

2. Install Air Pumps

Air pumps, as the name implies, are made to pump air into your fish tank, increasing oxygen levels. Air pumps are a simple way to add more oxygen to your fish tank because they use air stones to release oxygen into the water. The bubble it releases also breaks up the surface above, which increases agitation resulting in more oxygen in the water.

3. Install Spray Bars 

Spray bars work by spreading water around the whole fish tank. It helps the water gently move around and stirs up the surface, which increases the amount of oxygen dissolved in the water. Because of the movement of the water, it also relieves pressure from the filter.

4. Add Plants

There are many reasons why you should add plants to your aquarium. They improve the water and stop algae from growing by using the nutrients in fish waste, uneaten food, and other organic debris. They make oxygen as long as you always make sure they get sufficient light.

5. Install Powerhead

Powerheads do a much better job of getting oxygen into the water and moving it around in the aquarium than air stones do. The water quality in an aquarium gets better the more the water is moved around and cleaned.

6. Keep Aquarium Temperature Cool

It has been observed by many aquarists that as the temperature of water rises, it can hold less oxygen. You can avoid this by not putting your aquarium in direct sunlight, which will keep it from getting too hot.


Can There Be Too Much Oxygen in A Fish Tank

It is also possible for there to be too much oxygen in the fish tank. Too much oxygen in the water can cause gas bubble disease, which can be fatal.

Will Your Filter Add Oxygen to A Fish Tank

Filters help to make more oxygen because they move water. As the water moves, the oxygen dissolves, adding more oxygen to the water.

Are Bubbles Good for Fish Tanks

Bubbles are good in fish tanks because they add oxygen to the water. But if there are too many bubbles, it could mean that the water has too much oxygen, which is bad for the fish.

How Can I Get More Oxygen in My Fish Tank without A Pump?

Besides an air pump, you can increase the amount of oxygen in your fish tank with spray bars, hob filters, and plants. Because the air and water are always mixing at the surface, dissolved oxygen levels are usually higher in flowing water than in still, stagnant water.


Oxygen is important in aquariums because it allows your fish and other animals to live. There may be times when you need to increase the amount of oxygen in your tank right away. You can easily do this by pouring water into the aquarium from up high or by stirring the water, making sure to disturb the surface water so that the oxygen in the air mixes with the water. You can also add oxygen to your aquarium water by placing air stones and installing HOB filters or spray bars. Just remember to keep the tank in good condition by changing the water and cleaning it, and giving the surface a good stir. This will make it easier for your fish to breathe.

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