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How Long Does An Oscar Fish Live? 21 Years?

How Long Does An Oscar Fish Live? 21 Years?

Image credits: Justin Bradley (CC license)

Do you know oscars are often referred to as water dogs? That’s because they wag their tails and shake their heads to greet their owners. And that’s not the only similarity oscars share with dogs. They have pretty identical lifespans, too. 

How Long Does An Oscar Fish Live?

Most oscar fish live for around 8-12 years on average. However, when given the right diet and care, they can easily live for about 15 years. The oldest known oscar fish reportedly made it to its 21st birthday! 

How Long Does An Oscar Fish Live In Wild? 

In the wild, oscars live up to 18 years. But this isn’t true for all fish. As a matter of fact, fish mature comparatively quicker in the wild and complete their lifespan sooner. 

How Long Did The Oldest Oscar Fish Live?

The oldest oscar fish recorded lived for 21 years. Give your fish the proper diet and emulate the right environment – and your fish just might break this record!

How Big Do Oscar Fish Grow?

Oscar fish grow anywhere between 11-15 inches (30-40 cm) on average. And their average weight is about 1.58 kgs in adulthood. 

Juvenile oscars most commonly available for sale are only about 1-3 inches long. 

How Fast Do Oscars Grow?

In the first year, oscars can grow as fast as one inch per month. The growth will slow down once they’re about 9-10 inches long. But it’s not uncommon to hear of an oscar hitting 12 inches by its first birthday! 

To help oscars live life to the fullest and longest, it’s essential to know the different diseases they’re susceptible to and how to tackle them. 

And that takes us to our next segment!

Oscar Fish Diseases 

The six most common diseases oscars are susceptible to are hole-in-the-head disease (HITH), bloating, fin rot, velvet disease, ich, and popeye disease. 

Hole-In-The-Head Disease 

Like most cichlids, oscar fish are prone to the hole-in-the-head (HITH) disease, which manifests as small holes in the area near the head and the face. As the disease progresses, there will be several pitted areas along the fish’s lateral side. The holes almost look like craters. 

The signs of HITH disease in oscars are:

  • Pitting and erosions along the head and the lateral line 
  • White sores near the eyes and on head 
  • Yellow or white mucus trailing from the pits
  • Loss of appetite 
  • Faded colors

Unfortunately, the main reason behind HITH disease is still unknown. The closest we have come to know is that the flagellate parasite Hexamita may cause it. 

Nonetheless, fish exposed to poor water quality, malnourishment, and overcrowding often contract this disease. 

How To Treat HITH Disease? 

If left untreated, HITH is downright fatal. However, since there’s no one definitive cause behind this disease, there’s no definitive treatment. 

Your vet will zero in on the potential triggers and usually recommend a multi-step approach. In most cases, the fish will be prescribed an anti-parasitic medication. 

You’ll, of course, have to remove any stress factors. It’s wise to transfer the bullies to another tank for the duration and be a step ahead of the water quality. 

A case report from the Iranian Journal of Veterinary Science and Technology has shown that this disease can reportedly be treated with a drug called Flagyl (metronidazole). 

Also, veterinarian Margaret A. Wissman shares you can administer metronidazole in the fish food if the fish has an appetite. Alternatively, she suggests a bath in metronidazole for six to twelve hours. The treatment usually lasts for 5-10 days, depending on the severity. 

But, of course, you should first discuss the best step forward with your vet before starting any medication on your own. 


Ich is hands down the most common aquarium disease, and your oscars are in no way immune to it. The classic symptom of ich is tiny white dots across the body. And the scary thing about this condition is that it can transfer to other fish without a host! 

The signs of ich in oscars are:

  • White dots like salt flakes all over the body 
  • Rubbing body against different surfaces 
  • Flashing 
  • Loss of scales
  • Panting 
  • Lack of appetite
  • Reddening of the gills and fins

The culprit responsible for ich is a protozoan parasite called ichthyophthirius multifiliis. This parasite has a super complex lifecycle and can proliferate in your tank in a jiffy – often leading to the sudden onset of the disease.

How To Treat Ich? 

If ich is not treated on time, all your aquarium fish will drop like flies. You can treat ich in several ways, like using malachite green, copper sulfate, salt, and formalin. 

It’s also advised to raise the water temperature by a couple of degrees when treating ich to speed up the parasite’s life cycle and lessen the time required for treatment. 

If you are interested to know more about the ich’s complex lifecycle and what we use to annihilate it, you might want to read this article

Fin Rot 

Fin rot is super common but also entirely preventable. Well, technically, fin rot is caused by one of many bacteria present in the tank. But the root cause is almost always a poor environment. 

And a poor environment could mean anything – for instance, an over-cramped tank, poor water quality, and low oxygen levels. 

The signs of fin rot in oscars are:

  • Discolored fin edges 
  • Frayed fins 
  • Parts of fins may fall off 
  • A slimy production from the fins
  • Affected area appears red and inflamed 
  • Bloody patches 

Ich is usually caused by one of the following bacteria: Flexibacter spp., Pseudomonas spp., Cytophaga spp., Aeromonas spp., and Flavobacterium columnarae. 

Over time, as the disease progresses, the fins will become shorter and shorter as dead flesh sloughs off the affected fin. 

How To Treat Fin Rot?

In most cases, the vet will prescribe over-the-counter antibiotics like tetracycline, chloramphenicol, and oxytetracycline to fight fin rot. But make sure you don’t administer these medications without consulting a vet first. 

In severe cases, your oscar fish may have to go through the knife to get rid of the infected tissue. 

In minor cases, the fish will successfully regrow the fins. 

And since in 9 out of 10 cases, fin rot is caused by environmental factors, it’s crucial to reevaluate the fish’s environment and make necessary changes.

Popeye Disease 

The popeye disease – technically known as exophthalmia – is characterized by swollen and abnormally protruded eyes that could be caused because of several reasons. However, in most cases, poor water conditions are to blame. 

The signs of popeye disease in oscars are:

  • Swollen or bulging eyes 
  • Cloudy eyes 
  • Fluid leaking from the eyes 

The swelling is usually caused by the fluid leaking into the area behind the eyeball. The eyes will also be cloudy or ruptured if the cornea is ruptured. 

If untreated, the infected eyes can rupture, and your oscar will be visually impaired for life. 

How To Treat Popeye Disease? 

Treatment for popeye disease will depend upon the underlying cause. Always consult a vet and zero in on what actually caused the disease. 

For instance, if the eye has been injured, the fish will need palliative care using aquarium salt. If it’s because of a parasitic infestation, the vet will prescribe certain antibiotics to treat the water. 

Since this disease almost always boils down to poor water conditions, perform regular water changes and monitor the water throughout the recovery time and beyond.

Your fish can go blind if you cannot provide timely treatment. While most fish can adapt to seeing from just one eye, things will get complicated if they lose vision in both eyes. 

Dropsy Or Bloat 

Dropsy or bloat is characterized by swollen bellies. It is a grave yet common health condition that can be triggered by a multitude of reasons. Actually, dropsy or bloat is a cluster of symptoms triggered by a bacterial infection. 

The bacteria that causes dropsy is almost always present in the tank. And while healthy fish seldom fall prey to this disease, those with compromised immunity will easily contract it. 

The signs of dropsy or bloat in oscars are:

  • Swollen abdomen
  • Bulging eyes 
  • Stringy and pale feces 
  • Red and swollen anus 
  • Erratic swimming patterns 
  • Clamped fins 
  • Curved spine 
  • Ulcers on the body

How To Treat Dropsy Or Bloat?

Annihilating the bacteria that causes dropsy is extremely difficult. Therefore, some experts suggest euthanizing the fish so the disease isn’t spread to other fish. 

To treat the fish, transfer it to the hospital tank immediately first. Next, add 1 tablespoon of salt per gallon of the water to give the infected fish a salt bath. 

You can also treat the food or water with antibiotics as suggested by the vet. Test the water parameters of the hospital tank daily. 

And if you think the bloating is caused by a digestive problem, fast the fish for a couple of days, and break the fast with cooked and skinned peas. 

Relevant Readings!

Salvini Cichlid Care Guide | Diet, Habitat, Breeding, Accessories

Can Cichlids Live With Tetras? Here’s Why They Can’t!

How Big Do Jewel Cichlids Get? 4 Tips To Grow Them Fast!

How To Help Oscar Fish Live Longer?

two oscar fish
Credits: kcblanchett (CC license)

There’s no one magic formula to help your oscar live longer, nor is there any rule set in stone. Instead, factors like emulating the best possible environment, providing the biggest tank possible, feeding the proper diet, and staying on top of water parameters and potential diseases play pivotal roles. 

Let’s have a brief look at them! 

Providing The Biggest Tank Possible

Oscars are big fish – sorry, you already know that. In captivity, they usually grow between 10-12 inches. Therefore, the absolute minimum tank size recommended for a single oscar is 55 gallons. 

But I recommend at least 75 gallons for a single oscar. And add a minimum of 30 gallons extra for every new addition. 

Whenever possible, go for a bigger tank. I’ll tell you why. 

Although there’s no scientific backing, it’s a firmly held belief in the hobby that the fish grows to the size of its tank. 

In a small tank, a fish will not get enough exercise it requires to grow naturally. As a result, the growth will abnormally be stunted. 

Also, the smaller the tank, the more temperamental it is. 

Oscars love to eat and will produce a sizable amount of bioload every day. If the tank is small, it will become polluted a lot quicker. And as I always say, dirty water is a fool-proof recipe for diseased fish. 

Studies have also shown that if the tank is cramped, fish produce a stress hormone called cortisol, which suppresses their appetite and reduces their ability to transform food into energy. 

And a lesser-known reason you should opt for a bigger tank is to dilute the growth-inhibiting hormones and pheromones these fish release into the water. Yes, you read it right. 

Like most fish, oscars release certain hormones and pheromones in the water that can stunt the growth and negatively affect the health of other fish. If your tank is big enough, the hormones will get diluted and become less effective quickly. 

Hence, you should never skimp when getting a tank for your oscar. 

And by the way, oscars are prolific jumpers. So you’ll need to get a tank with a robust lid. 

Maintaining The Right Water Parameters 

Here’s a quick view of the ideal water parameters for oscars:

Temperature 74-81°F
pH 6-8 pH
General Hardness 100-200 ppm
Carbonate Hardness 80-90 ppm
Ammonia Ammonia 0-0.25 ppm
Nitrite 0 ppm
Nitrate Below 20 ppm
Phosphate Below 0.5 ppm
Water Movement Moderate-high

As with all fish, the water quality plays a tremendous role in determining how long your oscar will live. Especially since oscars produce a large bioload, you will need help from a robust filtration system to maintain the water quality. 

Many aquarists recommend combining the power of a canister filter and a hang-on-back (HOB) filter to manage the water quality. 

Also, don’t skip water changes. Perform at least 25-30% water change every week or more, depending on your stocking number. 

Since oscars are messy, harmful spikes of compounds like ammonia and nitrite happen a lot quicker in the tank. So, there’s always a heightened chance of your fish falling victim to toxic poisoning. 

Symptoms of ammonia poisoning in oscar fish are lethargy, clamped fins, erratic swimming, gasping, and inflamed gills. 

And some signs of nitrite poisoning in oscar fish are rapid gill movements, panting, loss of buoyancy, listlessness, brown gills, and getting curled head to toe. 

Since oscars are tropical fish, they’re susceptive to changes in water temperature. So don’t shy away from investing in a reliable heater. 

If the water is too hot, the oxygen level will deplete, and your fish will suffocate. You will also find your fish lying quietly at the bottom, since the base will be comparatively more oxygenated than the surface. 

On the flip side, if the water’s too cold for the fish’s liking, it will compromise its metabolism and make it sluggish. 

Feeding The Right Diet

Oscars are omnivores but will prefer a carnivore diet over plant-based food any day. They’re also voracious feeders with enormous appetites. Overfeeding and underfeeding both can lead to grave consequences and cut your oscar’s life short. 

Therefore, put some effort into formulating the right diet plan for your fish. But, don’t worry – it’s not as hard as you think!

In the wild, oscars feast on small fish, larvae, crustaceans, insects, and plant matter. 

In the tank, the easiest option is to give store-bought pellets or flakes made specifically with oscars in mind. They’re formulated to contain all the nutrients your fish need. 

Also, don’t forget to occasionally supplement the diet with treats like frozen bloodworms, live fish, small crustaceans, and blanched veggies. Giving live food helps bring out and hone their natural hunting instincts, which can be pretty fun to watch! 

Several new studies have pointed out that the hole-in-the-head disease could be primarily caused due to poor diet. So, don’t forget to pay extra attention to what goes inside their tummy. 

As for feeding frequency, give 3-4 small meals a day an amount they can consume in about 30 seconds. 

Overfeeding is a common problem in the hobby. This makes the fish obese and the tank dirty. 

But underfeeding is just as big a problem. We’re often told to watch the amount we give for the sake of maintaining the water parameters.

So, we often end up underfeeding the fish. 

Malnourishment can lead to several grave consequences. For instance, lack of vitamin A leads to vision problems, impaired growth, internal bleeding, and appetite loss. 

Lack of vitamin D hampers growth, whereas vitamin E deficiency leads to muscular wasting. 

If you’re interested in knowing more about this topic, check out this article

Choosing The Right Tankmates 

The Oscars are aggressive and territorial. Thus, you should be really careful when selecting tankmates for them. Given their predatory instinct, adding any small fish or crustaceans means throwing them under the bus. 

Oscars are fierce but also social if kept in the right environment. On the other hand, if you add them with the wrong tankmates, they will only get stressed, which will shorten their lifespan. 

Some suitable tankmates for oscars are convict cichlids, firemouth cichlids, arowanas, bichirs, green terrors, jack dempseys, jaguar cichlids, severum cichlids, and sailfin plecos. 

The fish I mentioned above can hold their own against a cichlid. 

If kept with the wrong tankmates, your oscars will naturally be uncomfortable and stressed. This, in turn, will compromise their immunity and make them vulnerable to a plethora of diseases. 

Offering The Right Treatment And Care

I have already touched on the subject of various diseases that oscars are vulnerable to. Once again, they are hole-in-the-head disease, ich, fin rot, popeye disease, and bloating/dropsy. 

In most cases, the wrong water parameters are to blame. However, if you feed the right diet and maintain the correct water quality, the disease can be prevented 9 out of 10 times. 

And before you administer any medication, always make sure to discuss it with your vet first. Administering the wrong medicine can be deadlier than contracting the disease itself!

Final Words: How Long Does An Oscar Fish Live?

Oscars are hardy fish that enjoy a pretty decent lifespan. They live for around 8-12 years on average. However, in the wild, they can live up to 18 years. 

Maintaining the right water parameters, feeding the right diet, and providing a stress-free environment go a long way in extending the lifespan. 

And if you think your fish is not well, don’t administer the medicines on your own. Always seek medical advice first! 

Recommended Readings!

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