Oscar Fish Yawning – All You Need to Know

If you have Oscar fish or think about getting some, you probably have many questions about this species. Unlike many other fish species, Oscars bring something new to the…tank. They are highly intelligent and show personality, leading people to consider them part of the family.

It also helps that Oscars have a lifespan of up to 20 years. They are also capable of recognizing their handlers and showing excitement when getting their favorite foods.

Today, we will discuss one of Oscar fish’s intriguing behaviors – yawning. Do Oscars yawn and, if so, why?

Let’s have a look!

Do Oscar Fish Yawn?

Yes, like most fish. However, they don’t yawn for the same causes. In humans, yawning typically occurs as a result of slow breathing. Even more specifically, is the result of our bodies not getting enough oxygen. This will trigger the yawning that aims to bring in more oxygen and eliminate excess CO2.

Your Oscars yawning is typically a sign of environmental issues, disease, feeding problems, etc. This doesn’t happen with fish since they live in aquatic environments. Their breathing process is different since they breathe through their gills and the oxygen synthesis occurs differently.

It’s also not a legitimate yawn; it just looks like one. The fish will open its mouth widely, sometimes several times in a row, as if gasping for air.

Do Oscars Yawn When They Are Sleepy?

No, they don’t. Oscars, like all fish, require sleep and rest, but they don’t yawn like humans or other mammals. Typical yawning, as I’ve already explained, signifies low oxygen levels in the body or an accumulation of CO2.

The act of yawning is exclusive to creatures living on land. Aquatic creatures cannot display this behavior. Although, in some cases, it does look similar.

How Often do Oscars Yawn?

The answer depends entirely on the reason behind the behavior. The most common reason for yawning in aquarium fish is high levels of nitrates. The water quality is poor, leading to an increase in nitrates and lower oxygen levels.

Oscar’s yawning signifies discomfort, and it can repeat pretty often if things don’t change. In many cases, the Oscar can keep yawning even after you’ve performed the water change and things have returned to normal.

You shouldn’t worry, however. This is just a fallout behavior that will go away soon. The important thing to take is taking Oscar’s yawning seriously. The yawning behavior in fish isn’t as harmless as it is in humans. It usually suggests more serious underlying problems that need an immediate solution.

Why Do Oscar Fish Open Their Mouth?

You may have already noticed this behavior in your Oscars but didn’t think much of it. Like pretty much all fish, Oscars will open their mouths occasionally; it’s nothing to worry about. The problem arises when they do it often.

Here are some of the potential causes to consider:

– Poor Water Quality

This is the number one reason why the majority of aquarium fish face health issues and even death. The water’s quality will drop for a variety of reasons, but there are 3 that outweigh all the others:

  • Overcrowding – Too many fish into a too small space. This will spell disaster in the long run, as overcrowding will increase the fish’s aggression and lead to faster accumulation of fish waste. This isn’t necessarily an issue if you change the tank’s water regularly. If you don’t, the fish waste will increase the ammonia levels, poisoning the water and killing the fish.
  • Overfeeding – Giving your fish too much food can backfire fast. We’ll skip the fact that overfeeding will cause your fish to experience digestive issues, including constipation, and jump to the essential. Excess food leftovers will accumulate on the substrate and decay, increasing the levels of ammonia and nitrates. These substances can be fatal in large enough doses, and frequent yawning is one of the first signs your Oscars feel their effects.
  • Dirty aquarium – Not cleaning your aquarium regularly translates to dead plants, fish waste, food residues, and even dead fish decaying in the water. This can increase the ammonia levels fast, affecting the entire fish population.

– Lack of Oxygen

Oscars will yawn and gasp for air if the water has low levels of oxygen. You should see them going to the surface and moving their mouths frantically. When that happens, you know that the oxygen levels are dangerously low.

Performing a water change should fix the issue. To prevent the same problem in the future, perform water changes regularly, at least once per week. You may need to do it more often if you have a lot of fish.

– They Want to Eat

Oscars will inform you that they’re hungry in case you don’t pay attention to their feeding schedule. They will open and close their mouths more rapidly, simulating the feeding behavior.

If they show no other symptom of distress, they’re simply hungry.

– Stress or Disease

Oscars can grow stressed for a variety of reasons. These include parasites, low oxygen levels, ammonia buildup, bullying, etc. They will display similar behavior when dealing with infections and diseases, which is why you should always take them seriously.

Some of these health conditions can prove deadly fast and spread to other tank inhabitants. Isolate the fish, assess its symptoms, and provide adequate treatment for 1-2 weeks.

If the fish overcomes the disorder, you can reintroduce it to the main tank. If not, euthanasia is your only option left.

– High Temperature

The higher the water temperature, the lower the oxygen level. The ideal environmental temperature for Oscars sits at 74 to 80 F. It’s similar to that of guppies.

If the water temperature exceeds the upper limit by too much, the fish will display signs of discomfort. Long-term, high water temperature will drop the oxygen level, increasing your Oscars’ discomfort and even leading to asphyxiation.


Oscars will yawn for a variety of reasons. Unfortunately, sleepiness and tiredness are among them.

If you notice your Oscar gaping its mouth wide open like if it were yawning, investigate the causes. It may be something rather benign like mild stress or hunger or something more dangerous like ammonia buildup or accumulation of nitrates.

Take measures fast and solve the problem before it aggravates.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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