I get commissions for purchases made through links in this post. Learn more.

6 Easy Steps On How To Increase Oxygen in the Fish Tank

Keeping an aquarium is far too different from having your first goldfish in a fishbowl. You’d need to learn the various factors to keep fish alive in an aquarium.

One of the biggest mistakes most first-time aquarists do is not giving fish enough oxygen.

Having adequate oxygen in a fish tank is a crucial part of keeping fish happy and healthy. That’s why it’s essential to learn how to increase oxygen in the fish tank.

There are many causes of dropping oxygen levels in a tank. Fortunately, there are also ways to fix and prevent this problem.

Signs of Low Oxygen Levels

There’s a big chance that the oxygen level in your fish tank is already dropping without you knowing it.

Here are the signs to watch out for before it’s too late.

Lethargic fish

Are your fish not as active as they were in the month you got them? It may be a sign that they’re not getting enough oxygen.

Look at your fish’s swimming and eating habits. Check if they’re starting to swim and move around less as well as eat less than before.

It could be hard to spot this symptom in some fish. In this case, try to watch out for the other signs.

Labored breathing

Fish that have a difficult time breathing might not be receiving enough oxygen. See if the gills are moving more quickly.

This could be a sign that they’re trying to get as much oxygen as they could.

Try to observe if your fish are trying to reach the water’s surface often. It could mean that they’re gasping for air. But, don’t confuse this for times when they’re feeding.

These are the two signs that your fish aren’t getting enough oxygen. Once you notice these signs, you must move quickly to solve the problem.

Causes for Low Oxygen Supply

To solve the low oxygen problem in your tank, you should know the reasons behind it.

Learning the cause of the problem should help you decide on how to increase oxygen in the fish tank.


Imagine that you’re in a small room that can only accommodate 10 people. Now imagine that you’re in that room, but you’re with 20 people inside.

Besides being uncomfortable, you’ll find yourself having a hard time breathing.

This goes the same for your fish. When there are more fish than the recommended capacity of your tank, the fish will not get enough oxygen.

They’ll be sharing oxygen that won’t be enough for all of them.

High water temperatures

As an aquarist, you should know the right water temperature for your aquarium. Some fish may need warmer water.

But, water that’s too warm for your fish could also cause low oxygen levels.

Warm water can’t hold as much oxygen as cold water. This is why some fish die especially during extreme summer weather.

Stagnant water

Water needs to constantly move to spread oxygen throughout the tank. The surface of the water has the highest oxygen levels. Without movement, the oxygen won’t go deeper into the water.

Large fish tanks without any water movement would likely have low levels of oxygen.

Too Much Waste

Wastes from fish, algae, and other components can also lower the oxygen levels in your fish tank.

The wastes decompose and create CO2. Too much carbon dioxide means not enough oxygen which is harmful to your fish.

Live plants with low lighting

Having live plants in aquarium is one way on how to increase oxygen in the fish tank. Live plants use the CO2 in water and release oxygen. But, they need light to process the CO2.

Without adequate lighting, live plants won’t be much help and can do more harm. Plants without enough light could deplete the oxygen content of the water.

Water additives and treatments

Some aquarists use additives to make water more ideal for fish. But, some of these chemicals can also harm the oxygen levels in the fish tank.

A tank may have one or all of these causes. It’s best to determine the root cause of the depleting oxygen to know how to fix them.

If you’re not sure what the problem is, try all the solutions listed below. This will help you ensure that you didn’t miss any of the causes above.

Step-By-Step Guide on how to increase Oxygen in the Fish Tank

It’s a good thing that there are many ways to improve oxygen levels in your fish tank.

With these simple steps, you can aerate the tank water to create a healthier environment for your fish.

1. Solve overcrowding

Overcrowding is one of the most common reasons for low oxygen levels in fish tanks. You must first determine how many fish should be in your fish tank.

Follow the general rule of 1 gallon or 4 liters of water for every 1-inch of fish. Transfer other fish in another tank to prevent overcrowding.

2. Check the water temperature and make adjustments

[amazon box=”B01A0TMS6Y”]

Different kinds of fish species have various needs. One of their basic needs is the right water temperature.

It’s important to always check the temperature every day. The water’s temperature mustn’t go over the fish’s ideal environment.

The oxygen becomes low when the water temperature is too high. Always use an accurate aquarium thermometer so you can always monitor the temperature.

Once you find out that the temperature is too high, try to do some quick fixes. Here are some of the easiest solutions to rising water temperatures.

  • Turn off or reduce the light of the aquarium.
  • Keep the tank away from direct sunlight. It’s best to keep it in the coolest part of your home.
  • Remove the tank’s lid. But, make sure that your fish are safe from predators.
  • Use a fan to blow across the tank’s water.
  • Change the tank’s water frequently with a mix of cool water.
  • Use an aquarium chiller to cool the water down.

3. Create more movement in the water

[amazon box=”B0036S70ZG”]

Increase the movement of the water to increase oxygenation. Using powerheads is an easy way to create movement in the water.

If you already have a filter and your fish still doesn’t get enough oxygen, you may want to add a powerhead.

If you have a large tank, you may want to use more than one powerhead. Put some powerheads on different parts of the tank so there’s water movement throughout the tank.

Using airstones or air pumps  would also work wonders.

Video: “Water Circulation in a Planted Tank – Hydor Koralia 240 nano”

4. Proper and frequent tank cleaning

Regular fish tank cleaning is a must. It’s not only to keep bacteria from making your fish sick. But, it’s also to maintain the oxygen levels in the tank.

Here are the steps on how to clean a fish tank properly.

1Except for the fish, water and pebbles, remove everything else from the tank — decor, filters, etc. Make sure that your hands are clean and free from soap and chemicals when doing this.

Get a smaller clean container for temporary storage for your fish. Transfer some of the water from the tank you’re about to clean to the temporary container. Then, use a fish net to scoop and transfer the fish to the container.


Save half of the remaining water in the tank. Set this aside because you’ll need it later. Fish need a certain amount of bacteria to survive.


Pour out the remaining water in the tank down the sink. Make sure that none of the pebbles get into the sink.


Use a paper towel to wipe all the sides of the tank. Don’t use any chemicals or soap. Doing this can harm the life of your fish. If the tank becomes dry, wet the paper towel with tap water. Wipe away all residue and traces of algae.


While the pebbles are in the tank, fill it up with tap water until they’re submerged. Move the tank back and forth swishing the pebbles. Pour out the water with the debris from the pebbles. Repeat this step until the water becomes clear.


For decorative pieces, use a toothbrush only for tank cleaning. Use it with tap water to scrub the crevices of the decor. Make sure that no algae remain on the decorations.


Pour the tank water you set aside earlier back into the cleaned tank. Then, fill it with the usual aquarium water you use. Make sure to leave some room for the water from the temporary containers with the fish.


Place all the decor and aquarium equipment back in the tank.


Finally, place the fish back in the tank carefully.

5. Solve the problem with live plants in your tank

If you’re using live plants in your fish tank, you should know how to manage them well.

If not, they’ll suck out more oxygen in the water leaving little to none for your fish.

There are two ways to solve this problem:


Add more lights. This will help the live plants absorb more CO2 and provide more oxygen. Make sure to place the lights evenly across the tank. You can put more lights in the areas where the live plants are.


Remove some of the plants. Try to balance the number of live plants to your fish. If you’re after the aesthetic aspect of the plants, try to replace some of them with artificial plants.

If you can’t handle caring for live plants, you can replace them completely with artificial plants. Doing this will not harm the oxygen levels in your tank.

You also won’t need to use a lot of lights which can increase the temperature of the water. But, you must use other methods to improve the oxygen levels in the tank.

6. Read the labels of additives and treatments

Before adding any additives or treatments to your fish tank, always read the labels. Make sure that they won’t interfere with the oxygen levels in your tank.

If you’re already using one, try to check the label and replace the product if it’s harming the oxygen level in the tank.

Follow these steps to solve the oxygen problem in your tank. You may try to skip some of the steps if you’re sure what caused the problem in the first place.

Still, trying to do these steps may not only improve the oxygen levels in your tank. It could also enhance the overall health of your fish and condition in the tank.

How To Prevent Oxygen Problems in Fish Tanks

Once you’ve learned how to increase oxygen in the fish tank, you must learn how to prevent it from happening again.

It’s best to monitor the dissolved water levels in the fish tank to ensure it’s normal. If you can spare some extra cash, you may buy a dissolved oxygen meter. This can accurately tell you if the oxygen levels are low in the tank.

To maintain healthy oxygen levels in your fish tank, remember to do these preventive measures.

  • Keep the right number of fish in the tank. If you want to get more fish, get a bigger tank.
  • Use adequate lighting to maintain the temperature in the tank.
  • Take care of live plants in your tank properly.
  • Regularly clean the fish tank. If possible, try to do it every week. This will ensure the cleanliness and adequate oxygen levels in the tank.
  • Use powerheads, air pumps, or air stones in your fish tank. Movement is important, so keep the water moving.


Keeping a fish tank isn’t as easy as you think. It needs a lot of time, dedication, and knowledge.

The oxygen level in your fish tank is only one of the factors you must monitor. You must keep the oxygen levels normal in the tank. Doing this will help in making your fish healthy and live a longer life.

Watch out for the signs of depleting oxygen in your tank. Invest in equipment if needed and do necessary actions once you find out there’s a problem.

Remember that prevention is key. Proper care of your fish and your tank will lower the risks of this problem from happening.

Follow the steps above on how to increase oxygen in the fish tank and the preventive measures to keep your fish happy and healthy.

Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

Aqua Movement