How I Easily Helped My Corydoras That Were Breathing Fast!

The primary reasons for fast breathing in corydoras typically include poor water quality, insufficient oxygen levels, temperature fluctuations, and stress.

Recently, I swapped out the filter in one of my aquariums. The previous filter, an internal one, seemed to create too strong a water flow for the tank’s needs, so I replaced it with a standard sponge filter.

Soon after the change, I observed that all my corydoras were unusually lethargic, often displaying rapid breathing while resting on the tank substrate.

Interestingly, the other fish in the tank appeared unaffected, behaving as usual. Nonetheless, I decided to investigate further to identify any potential issues affecting my corydoras.

As it turned out, the rapid breathing was due to low oxygen levels in the tank. After replacing the new filter with a sponge filter equipped with an airstone, my corydoras’ behavior returned to normal within a few days.

What Does It Look Like When A Corydoras Is Breathing Fast?

My Corydoras Breathing Fast

Recognizing a corydoras experiencing rapid breathing is straightforward, evident by the quick movement of its mouth and gills.

While I had observed this behavior in one or two corydoras previously, I had interpreted it as excitement, particularly during feeding times, when the fish would swiftly return to scavenging for food once pellets were dispersed onto the substrate.

However, this time, the situation seemed different. All six of my corydoras were exhibiting rapid breathing while resting on the tank substrate for prolonged periods without much movement.

Occasionally, some of the corydoras would dart to the tank surface to gulp air, a typical behavior for the species. However, it appeared that they were doing so more frequently than usual, suggesting a potential issue with oxygen levels in the tank.

Why Is My Cory Catfish Breathing Fast?

Common causes of corydoras catfish breathing fast include:

  • Poor Water Parameters
  • Low Oxygen Levels
  • Temperature Problems
  • Stress
  • Disease
  • Chemical Exposure
  • Problems With pH Levels
  • Overcrowding
  • Excitement

Here is a short explanation of each of these so you can investigate these potential problems in your own tank if you notice that your cory catfish is breathing quickly.

Poor Water Parameters

The health of an aquarium is largely determined by its water parameters.

When it comes to Corydoras, high levels of ammonia, nitrite, and nitrate are particularly harmful. These nitrogen compounds, when elevated, affect the gills of fish, making oxygen extraction difficult.

Recommended water parameters for different types of corydoras can change slightly but here are the water parameters for the corydoras aeneus that I keep in my tanks.

Water Temperature68 to 82 °F (20 to 28 °C)
Water FlowStill-Moderate
GH2–30 dGH
KH2-15 dKH
Ammonia0 ppm
Nitrite0 ppm
Nitrate<10 ppm
Corydoras Aeneus Water Parameters

Low Oxygen Levels

In an aquatic environment, sufficient oxygen levels are crucial for fish to thrive.

Stagnant water, which lacks proper circulation, restricts the exchange of oxygen at the surface, reducing dissolved oxygen levels in the water.

Additionally, a tank with a high bio-load, including both fish and beneficial bacteria, can consume oxygen at a rate that outpaces its replenishment, causing fish to breathe more rapidly to compensate.

Temperature Problems

Temperature plays a crucial role in fish health and elevated water temperatures not only reduce the water’s ability to hold dissolved oxygen but also increase the metabolic rate of the Corydoras, making them demand more oxygen.

Additionally, sudden temperature fluctuations, either up or down, can be particularly stressful for fish, leading to increased respiratory rates as they try to cope with the change.

The effect of temperature that did exist manifested as an increase in group air-breathing frequency at 30°C.

National Library Of Medicine

A study by David J McKenzie found that the test group’s corydoras would breathe faster and dash to the surface to breathe air more frequently when kept at higher water temperatures.


Corydoras are peaceful fish and can easily become stressed in adverse conditions.

Whether it’s due to aggressive tankmates, frequent and abrupt changes in their environment, or improper acclimation to a new tank, stress can manifest itself in the form of rapid breathing.

It’s essential to minimize these stressors and monitor the fish for signs of discomfort.


Just like any other living being, Corydoras can fall prey to various diseases. Respiratory issues brought about by gill parasites like flukes can make breathing a laborious task for these fish. Additionally, bacterial and fungal infections that impact the gills or the respiratory system can lead to rapid and labored breathing. Regular observation and prompt treatment are essential in these cases.

My corydoras breathing fast
My Corydoras Breathing Fast

Chemical Exposure

Aquariums are closed systems, and any chemical introduced can have a lasting impact.

Whether it’s an overdose of medication or the accidental introduction of detergents or other contaminants, chemical exposure can be toxic for Corydoras.

It’s always vital to ensure any chemical or medication added is safe and in the correct dosage.

Problems With pH Levels

The pH level of the water, indicating its acidity or alkalinity, can have direct effects on fish health.

Corydoras prefer specific pH ranges, and when water becomes too acidic or alkaline, it can lead to stress and discomfort, often evident through rapid breathing.

Regularly testing and adjusting the pH can help in maintaining a stable environment for the fish.


A densely populated tank can lead to various issues, including competition for resources and reduced oxygen levels.

When Corydoras are in an overcrowded environment, the increased competition and reduced available oxygen can cause them to breathe faster.

It’s essential to ensure that the tank size is appropriate for the number of inhabitants.


Like all creatures, Corydoras can display increased activity and faster breathing due to excitement.

This could be due to factors like feeding time, introduction of new tankmates, or changes in the environment.

Typically, this is temporary, and once the cause of the excitement subsides, their breathing rate should return to normal.

After testing my aquarium water to ensure that my corydoras were not breathing fast due to water parameters and quickly going over the other potential problems, I settled on oxygen levels being the cause of the problem.

How I Helped My Corydoras That Were Breathing Fast!

Getting An Airstone
An Air Stone

Fortunately, I have several spare air stones and an available output on my air pump, allowing me to introduce an airstone to my tank to observe if it can aid my corydoras in resuming normal breathing.

I added a length of airline tubing to my air pump, placed the air stone on the other end, and lowered it into my aquarium.

My goal was to create as much surface disturbance as possible to try and increase the exchange of carbon dioxide and oxygen in the tank.

Remember, I also had a new sponge filter and plenty of live plants in the tank, so I was optimistic that a single air stone would be able to elevate the oxygen levels, enabling my corydoras to breathe normally.

Air Stone In The Tank

It took less than 24 hours for my corydoras to increase their activity levels and although they would still lay on the substrate and breathe quickly, they would also move around the tank more frequently than they previously had.

This gave me hope that the rapid breathing of my corydoras was due to the oxygen levels in their tank and that the air stone was helping to correct the issue.

Within three days of adding the air stone to my tank, all of my corydoras had returned to their regular activity levels and the rapid breathing had stopped.

An Active Corydoras

I ordered a AQQA Sponge Filter that I reviewed in this article as a permanent way to increase the surface disturbance in the tank and maximize the exchange of carbon dioxide and oxygen to prevent the problem from occurring again.

The filter is cheap, comes with a ceramic media compartment in the base of the filter to help with your beneficial bacteria populations, and has a built-in air stone to increase surface agitation making it the perfect option.

Once the filter was delivered, I removed the air stone from the tank and attached it’s airline to the AQQA sponge filter, and placed that into my tank.

My New Filter

My AQQA sponge filter has been in the tank with my corydoras for over a month now and I haven’t noticed any problems with rapid breathing since increasing the surface disturbance in the tank.

If you notice that your cory catfish are breathing rapidly in your tank and there are no obvious problems with water parameters or stress then it may be worth adding an air stone to increase surface disturbance to see if there is a lack of oxygen in your aquarium.

Final Thoughts

I discovered that my corydoras were breathing rapidly due to low oxygen levels in their tank.

After some investigation, I found that adding an airstone to the tank significantly improved the oxygen circulation, leading to the normalization of his corydoras’ behavior in less than three days.

If your cory catfish are breathing quickly without evident stressors or water parameter issues, increasing surface agitation might resolve the problem.