How to Increase Oxygen in Fish Tank? (2 Effective Ways)

how to increase oxygen in fish tank

Just like us, fish need oxygen (O2), particularly dissolved oxygen, to breathe and perform cellular respiration. The lack of oxygen in fish tanks can cause fish to die.

How to increase oxygen in fish tank? You can instantly get more oxygen in the fish tank by increasing water movement, performing a large water change, or adding fish tank oxygen tablets. These are the fastest ways to boost oxygen for aquarium quickly.

Indeed, there are various short-term uses and different methods to oxygenate your fish tank for the long term, keep reading!

Short-term Ways to Increase O2 in the Fish Tank


What to prepare

Gather the following items to boost O2 levels in an emergency.

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  • A cup of water
  • Clean water
  • Ice cubes
  • Aquarium-powered air pump


1. Increasing Surface Agitation


Increasing water movement is one of the fastest ways to boost the oxygen for fish tanks at home. There are two most common methods to increase surface agitation:

[su_highlight background=”#c2ecfa” class=”nbhl”]01[/su_highlight]Pouring water directly to the tank

This oldest trick still works well when it comes to increasing the 02 levels in an emergency situation.

Fill a cup or a small pitcher with some aquarium water and slowly pour water from a height (just like a rainfall) into the center of the tank. Doing this will help to create bubbles that aerate the water and increase dissolved oxygen.

[su_highlight background=”#c2ecfa” class=”nbhl”]02[/su_highlight]Stirring water manually:

Another way to add oxygen to fish tank fast without a pump is to stir the water manually. Stirring water will increase aquarium aeration which produces O2 and allows it to get spread across the entire tank.

2. Doing a large water change

As waste accumulation can weaken the oxygen-carrying capacity in the tank, which leads to the lack of O2, performing a large water change is advisable to handle this problem.

To raise the O2 concentration in your tank, it’s better to do a 30-50% water change and replace it with fresh water. Be sure to add dechlorinated tap water, don’t disturb your gravel bed, and don’t add plants or fish while doing this method.

3. Adding ice cubes

In case the O2 levels in your fish tank are low because of high water temperatures, you should cool it down gradually by adding a ziplock bag of ice cubes. Putting ice cubes in a locked bag will prevent them from melting into the tank’s water and introducing harmful bacteria.

As cold water typically holds more dissolved oxygen content than warm water, it’s important always to keep the aquarium water at a suitable temperature.

4. Using an aquarium-powered air pump


Electric-driven air pumps don’t run in case of an emergency power outage which can cause an oxygen shortage in your fish tank. As a result, you should always keep a battery-powered air pump at home for this situation.

However, these types of battery-powered air pumps tend to be smaller which may result in a weaker water flow than electric air pumps. If you have a big aquarium, having more than one pump is recommended to sufficiently oxygenate water for fish.

It is also advisable to prepare extra batteries around as they can only run for a certain time, one may not be enough!

5. Adding fish tank oxygen tablets

One more way to oxygenate my fish tank quickly is to use oxygen tablets. However, this method is not common as it is only used for a really short term that is up to 3 hours at max.

You also can use aquarium air stones to increase oxygen in your fish tank.

Long-Term Ways to Increase O2 in the Fish Tank

1. Using a hang-on-back (HOB) Filter


When it comes to adding oxygen to fish tank, the HOB filter works well as an oxygenator. It works by drawing water into the filter, then releasing it via the filter outlet from a height to create turbulence in the water and distribute the O2 throughout the aquarium

In general, a HOB filter is a great way to increase oxygen for aquarium as it is so convenient and doesn’t take up too much space.

2. Using a Spray bar

The spray bar is used to agitate the tank surface which helps to increase oxygen levels in your aquarium.

The spray will be installed in the filter outlet of the canister filter, and spray the water across the surface of the aquarium to create water movement, which, as we know, allows more O2 to enter the water.

3. Using Aquarium Air Pumps


To get more oxygen in a fish tank, it’s important to improve water aeration. A fish tank oxygen pump is good for the job.

This equipment is designed to put more oxygen in fish tank by creating air bubbles rising to the tank surface and distributing O2 into the entire aquarium.

In general, large tanks are more likely to need an air pump than small-size ones. This is because a large amount of fish in a large tank can lead to poor water quality which causes a dangerously low oxygen level.

It’s also crucial to use this tool properly to maximize the oxygen exchange by putting the pump in an area where bubbles can break the surface tension easily.

4. Installing Fountain Heads​​

To add oxygen to a fish tank, many aquarists also use a fountainhead in their fish tank.

Not only used for pond aesthetically purposes, but fountains also help to improve O2 levels in the entire tank by agitating the water’s surface. This tool is absolutely useful when it comes to assisting in building a healthy aquatic ecosystem.

It’s also important to pick a fountainhead that fits your tank dimensions and comes with an adjustable flow rate.

Why Oxygen Deficiency in Fish Tank?


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  • Overstocking: One of the most common causes of the shortage of O2 is overstocking. It’s important to keep an appropriate amount of fish in your tank. Don’t let O2’s consumed rate bigger than the replenished rate.
  • High water temperatures: Warm water holds less oxygen than colder water. In addition, fish are likely to become more active in warm water and require more oxygen. As a result, there often won’t be enough oxygen for fish in high-temperature water which can lead to suffocation.
  • Lack of surface movement: The lack of water movement also causes oxygen deficiency in the fish tank because water movement is required to aerate the water and increase O2 levels.
  • Poor tank maintenance and cleaning: Excess waste accumulation due to the lack of cleaning, overfeeding and other debris can lower the oxygen-carrying capacity in the water while increasing ammonia levels.


Signs of Low Oxygen Levels in Aquariums

  • Less active movement: If you notice your fish start swimming slower or moving less than normal, that could be a sign of less oxygen in your fish tank. When there is not enough oxygen in the water, they will start losing their energy to move around.
  • Fishes gasp at the water’s surface: Only some fish species like dwarf gourami get oxygen from the water’s surface, while others will congregate at the tank surface, where O2 levels are highest to gasp if your aquarium no longer has enough O2.

In this case, it is recommended to do a large water change to bring dissolved oxygen to the tank in time.

  • Labored breathing: Labored breathing in fish includes a sign of more rapid gill movements. This is because fish get more oxygen through their gills to breathe. The low oxygen levels in the tank make them have to move their gills faster to take more oxygen from the water.



Where do the fish get oxygen from the reef tank?

In fact, fish don’t get oxygen directly from the water, they absorb O2 from the surface air. This is because the oxygen in water is naturally locked with hydrogen, and fish can’t split the O2 separately to utilize it.

To get oxygen into fish tank, it all relies on the gas exchange process between the water and the air via surface agitation. This process will allow CO2 to be released from the water to the air and more oxygen to be dissolved into the water.

How much oxygen does a fish need?

Fish need enough dissolved oxygen to breathe and stay healthy, however, each fish species requires different oxygen levels.

Generally speaking, a healthy fish tank should have 80-110% oxygen saturation while the DO level should be 6-8 mg/L. So you should test oxygen levels in your aquarium frequently to maintain a good O2 level.

Be careful with gas supersaturations (above 115%), occurring when the water holds more gas than usual, which will cause gas bubble disease in fish with high mortality.

Can I add too much oxyzen in a aquarium?

You can not add too much oxygen to an aquarium. Although oxygen is vital for fish to breathe, too much of it can cause gas bubble disease or hyperoxygenation, which is harmful to fish and other aquatic inhabitants.

A healthy fish tank should have a good balance of O2, CO2, and other chemicals, or it might become a deadly aquatic environment.

Check this article to find out how the CO2 regulator helps your fish tank’s ecological balance.

How long can fishes live with no oxyzen?

In general, fish can only survive from a few minutes up to a couple of days at max without oxygen in the aquarium.

However, how long they live without O2 also depends on which type of fish, their health, and their age. Some species like goldfish can live in low O2 water conditions for over 5 months.


How to increase oxygen in fish tank? Increasing water movement, performing large water changes, or using fish tank oxygen tablets are some short-term ways to boost O2 levels in your fish tank quickly.

However, it’s better to equip your aquarium with permanent methods from the beginning to stabilize the O2 level with spray bars, air pumps, or HOB filters.