Why is my Arowana Yawning & Breathing Heavily? (With Solutions)

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Arowanas are among my favorite types of fish. However, they are also quite expensive. That is why I get nervous when I see odd behavior that may potentially indicate a problem. For example, more than once, I saw that my Arowana keeps breathing heavily, yawning all the time. To solve that issue, I began to research the topic pretty extensively.

Arowanas typically to breathe heavily and yawn due to oxygen deficiencies. That typically occurs in overstocked tanks or in stagnant water that features high temperature. However, Arowanas also yawn due to high ammonia and nitrates concentrations, or a disease that had infected their gills.

As we move forward, I will present the steps you should take to ensure that your Arowana doesn’t yawn excessively. I will teach you how to solve the underlying condition, ensuring that your fish live long and healthy.

What Makes Arowanas Yawn & Breathe Heavily?

Fish are not like human beings. When they open their mouths, they are not necessarily yawning, not in the conventional sense. The habit is relatively common in fish, and it doesn’t mean anything unless it repeats.

If you have observed frequent yawning in your Arowana, the creature is probably struggling to breathe. Such behavior should worry you because it is indicative of a severe underlying issue, one that you must resolve quickly before your fish suffers permanent damage. Some common causes of yawning and heavy breathing in Arowana include:

1. Gills Washing

It is worth reiterating the fact that yawning isn’t always a sign of trouble. Sometimes, your Arowanas are merely flushing their gills.[1] Fish breathe by using their gills to draw oxygen from the water. Sometimes, debris obstructs the gills, impeding the fish’s ability to breathe. 

Arowanas can clear these obstructions by sucking water into their mouths and flushing it out through the gills, cleaning them in the process. You should suspect that this is the case if you’ve noticed debris covering your Arowana’s gills, or if the tank is relatively dirty.

2. Oxygen Deficiency

If your Arowanas are seemingly yawning because they are struggling to breathe, you must consider the possibility that your tank has an oxygen deficiency. Oxygen deficiencies can be imputed to a variety of sources.

For instance, hot water doesn’t hold as much oxygen as cold water.[2] If the summer heat has raised the temperature in your tank, the water’s oxygen levels will fall, causing the Arowanas to gasp for air. That also happens if the tank is exposed to direct sunlight.

You can expect similar results whenever your heater malfunctions, raising the tank’s temperature without your knowledge. If the temperature isn’t at fault, look at the filter. When working correctly, filters consistently remove waste from the water.

They also agitate the water, not only increasing the rate at which oxygen dissolves but also making sure that it is distributed throughout the aquarium. Oxygen levels are usually insufficient in stagnant water, and that is what you will get when the filter stops working.

3. High Ammonia Levels

Ammonia is a deadly toxin that can kill your Arowanas. You have to keep the ammonia levels in your tank at zero. If the concentration of ammonia is allowed to rise, your Arowana’s health will suffer. The substance will burn your fish’s gills, affecting its ability to breathe and causing the Arowana to gasp for air.

Suppose you have eliminated the possibility of an oxygen deficiency in the tank, but your Arowana is still yawning and breathing heavily. In that case, you can comfortably conclude that the creature’s ability to breathe has been compromised by ammonia poisoning. 

Nitrates are another element that can affect the Arowana’s ability to breathe, not to mention a high pH. These toxins usually rise in overcrowded and relatively small tanks. That also happens when the aquarium’s water is not replaced regularly.

4. Diseases

Suppose high concentrations of ammonia, nitrates, and nitrites have been eliminated as the potential source of your Arowana’s labored breathing, and your tank is clean and adequately cycled. In that case, you should look for signs of diseases and infections.

Some ailments can affect a fish’s ability to breathe. One example is gill decay. Caused by microscopic oval flagellate, the illness attacks the gills until they malfunction.[3] It also causes your Arowana’s colors to fade.

5. Overcrowded Conditions

If your Arowanas are healthy and all the water parameters are correct, you could still create an oxygen deficiency through overstocking. Like all fish, Arowanas extract oxygen from the water to survive. Unfortunately, many factors could lower oxygen concentrations.

For instance, if you have too many Arowanas, they will consume more oxygen than your tank can replenish through conventional means. That will naturally create an oxygen deficiency. That is also the case in aquariums that are stuffed with living vegetation.

How to Treat Heavily Breathing Arowanas?

If your Arowana is breathing heavily, you have to identify and resolve the issues causing this behavior. The solutions you deploy will vary depending on the causes you have identified:

1. Elevating Oxygen

If an oxygen deficiency in the tank is to blame for your Arowana’s labored breathing, you can increase the oxygen levels in the water by installing a filter, assuming you don’t have one. If you already have a filter, consider buying a more robust replacement. 

Get a filter that can create the sort of agitation that will ensure the oxygen reaches every corner of the tank. Since Arowanas require large tanks, you should consider a robust device, like the Fluval FX4 Canister Filter (link to Amazon). That one could agitate a 250-gallon tank pretty impressively and received numerous positive reviews online.

It would help if you also considered adding airstones. I would suggest scattering a few across the entire tanks in equal distances from each other. If your tank suffers from oxygen deficiencies, the more you add, the better. You can get the Pawfly 1 Inch Air Stone (link to Amazon) bundle, containing ten air stones for a relatively low price.

2. Reduce Temperature

Arowanas thrive in temperatures ranging between 75 and 86 degrees F.[4] If high temperatures are to blame for the oxygen deficiency in your tank, you can give your fish relief by turning the heater off and using a fan to blow across the water’s surface. 

It would be best if you also considered switching all the lights off. They tend to contribute to the overall temperature in the tank. If the situation is truly dire, add some ice cubes to the tank (make sure that you place them in zip-close bags beforehand). They will have a more drastic impact on the temperature than the fan.

3. Check for Ammonia

To combat ammonia, you have to perform regular water changes (that will also reduce nitrate and nitrite levels). Some tanks require thorough manual cleaning. You shouldn’t leave your tank’s hygiene in the hands of your filter. There are limits to what it can do. 

I suggest that you make a deliberate effort to remove waste and leftovers from the tank. As a rule of thumb, replace 10-20% of the water every 2-3 weeks. Otherwise, the leftovers will rot and raise the concentration of toxins like ammonia. Don’t stop at removing waste. Algae can also reduce the water’s oxygen, especially if it is allowed to overrun the tank.

The only way to prevent toxins from threatening your Arowana’s ability to breathe is to maintain a clean tank. However, that is an ongoing process. Without proper maintenance, oxygen deficiency in your Arowana tanks will become a frequent occurrence.

I also recommend checking the API Aquarium Test Kit (link to Amazon). That bundle will tell you if the ammonia, nitrates, nitrites, or pH are too high or low. Within minutes, you will know if something has gone wrong. You can use that kit in numerous tanks, and it lasts for a pretty long time.

4. Plants and Lightning

Plants are an interesting case. On the one hand, adding more plants to your aquarium can solve your oxygen problem. That is because plants consume carbon dioxide and expel oxygen, which is a good thing. But that is only in situations where they have been exposed to light.

In the dark, plants will become a threat to your tank by consuming oxygen.[5] In other words, if your aquarium needs oxygen, the addition of plants can make all the difference. But if you have too many plants and you realize that your aquarium won’t have sufficient lighting for extended periods, you can either reduce your plant population or increase the lighting.

5. Avoid Overfeeding

You shouldn’t overfeed your Arowanas, especially if your tank is overcrowded. The more food you give them, the more waste they produce. And as was noted above, waste is terrible for aquariums. When it rots, it contributes to the ammonia concentration in the water. 

The same is true for leftovers, which is why you have to feed your Arowanas in the right quantities. It would be best if you fed young Arowanas up to three times a day. Adult Arowanas should be fed once a day. However, in both cases, feed them no more than the amount they can consume within one to two minutes.[6]

You should also keep them in manageable numbers. If your tank is overstocked, none of the measures you take to increase oxygen in the water will make a difference. Your Arowanas will continue to yawn and gasp because the tank’s oxygen cannot sustain their numbers.

6. Disease Treatments

With diseases, the treatments utilized will depend on the sickness. Though, in many cases, you have to quarantine the sick fish (in case it shares a tank with other fish). Besides raising the temperature, carrying out water changes, and using aquarium salt, you have to match each illness to the appropriate drugs. 

Vets can help you here. They will point you towards the right medications to treat ailments like gill decay. Consider consultation if your Arowana also shows worrying signs, such as lethargy, pale colors, and abnormal swimming behavior.

What Are Typical Arowana Stress Symptoms?

Stress is another potential cause of labored breathing in Arowanas, though, in many cases, the fish won’t stop at merely gasping. It will also rush to the surface. Other symptoms of stress (besides gasping) include:

1. Hiding

Like most fish, stressed Arowana will spend a lot of time hiding. If you have plants and decorations in the tank, the fish will use them to stay out of sight.[7] That shows you that they do not feel safe in their environment, and they won’t emerge until that sense of insecurity disappears.

That behavior becomes more noticeable once you approach the Arowana’s tank. In some cases, the fish will also try to jump out of its tank. That is undoubtedly a situation you’d like to avoid since it often ends up with a dying fish.

2. Erratic Swimming

Erratic swimming behavior can also signify stress in fish. Some fish will rub their bodies against rocks, plants, decorations, and even the tank walls.[8] Others will swim up and down for no apparent reason. 

A few will hover in place or lie at the bottom. It mainly depends on the personality of your Arowana. However, if you’ve noticed changes in how your fish is swimming, it could indicate that it is stressed.

3. Loss of Appetite

Arowanas have a decent appetite. They are carnivores that eat snails, insects, small fish, and the like in the wild.[9] If your Arowana doesn’t have much of an appetite, you can conclude that it is sick or stressed. Stressed Arowana will either eat smaller amounts or ignore food altogether. As a result, they will become more inactive as their strength dwindles.

In some cases, an Arowana’s colors will fade in response to stress. This change is more comfortable to spot in fish whose scales are brightly colored. You can impute most changes in appearance or behavior to stress so long as you haven’t identified any signs that could point to a disease’s presence.

Though diseases can also cause stress, fortunately, with stress, once you eliminate the causes, the symptoms will disappear. For instance, if your Arowana keeps crashing against the tank walls because of toxins in the water, a water change will stop this behavior.

In most instances, if you can maintain optimal conditions in the tank while also eliminating all sources of danger, your Arowana will regain its peace of mind. However, if your fish fails to get back to normal despite your efforts, I suggest consulting a vet.

If you found this content useful, here is a related article that may also assist you:


Most commonly, Arowanas breathe heavily and frequently yawn due to oxygen deficiencies. They do so to exploit the oxygen residues presented in the water. However, that could also happen in oxygenated tanks, especially if the gills themselves are to blame.

If you’ve noticed dirt or debris upon the fish’s gills, you should perform more frequent water exchanges. You should also test the water’s basic requirements, including pH, temperature, nitrates, and ammonia. If none of these is the problem, consider consulting a veterinarian.


  1. https://fluffyplanet.com/do-fish-yawn/
  2. https://www.totalpond.com/blog/why-fish-gasp-for-air
  3. http://arowana8.tripod.com/Arowana/diseases.html
  4. http://www.aquaticcommunity.com/arowana/fish.php
  5. https://www.thesprucepets.com/low-oxygen-in-aquarium-water-1381215
  6. https://www.petco.com/content/petco/PetcoStore/en_US/pet-services/resource-center/caresheets/arowana.html
  7. https://petcentral.chewy.com/is-your-pet-fish-stressed/
  8. https://www.hartz.com/stress-in-fish-symptoms-and-solutions/
  9. https://www.fishkeepingworld.com/silver-arowana/