How big does an Oscar Fish get? Introduction to Oscar Fish

How big does an Oscar Fish get? Oscars are one of the most popular fish kept in home aquariums. They come in a wide variety of colors and patterns, and they’re usually quite friendly (though they can be territorial towards other fish). Oscars make a great addition to almost any tank, but you might want to know about the popular different types of Oscar fish available. In this blog post, we’ll take a look at eight common Oscar varieties. We’ll also include pictures of each type so you can identify them easily. So without further ado, let’s dive into our list!

How big does an Oscar Fish get?

Oscar fish, also known as the oscar cichlid or Astronotus ocellatus, can grow up to 12 to 18 inches in length and weigh up to 3 pounds. However, they typically reach 10 to 12 inches in length in captivity.

Oscar fish are popular freshwater aquarium fish that are known for their intelligence and hardiness. They are also known for their aggressive behavior, so they should not be kept with other fish that are smaller or weaker than them.

If you are considering getting an Oscar fish, it is important to provide them with a large tank that is at least 55 gallons in size. You should also make sure to provide them with plenty of hiding places and rocks to explore.

Oscar fish are carnivores and should be fed a diet of live food, such as brine shrimp, bloodworms, and feeder fish. They can also be fed a commercial diet that is specifically formulated for cichlids.

With proper care, Oscar fish can live for up to 15 years.

Oscar Fish

Introduction to Oscar Fish

Oscar fish are a longtime favorite in the aquarium hobby and one of the most popular freshwater fish period. These fish are big, colorful, and full of personality. So much so that they have been nicknamed the aquarium puppy or river dog by some due to their extremely playful behavior.

Like other popular freshwater fish, the oscar fish has been subjected to improper care by beginner and inexperienced hobbyists. Many first-time oscar owners are not aware of their true size and just how quickly they will outgrow a tank. If given the right care, these fish can fill a larger tank all on their own.

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The most popular type of oscar fish is the traditional orange and brown combination of the tiger oscar, but there are many varieties available for the more adventurous hobbyist.

Oscar Fish Care Requirements

Oscar fish are not impulse buys. They require long-term planning in regards to tank size, tank mates, and diet. Unfortunately, these fish are commonly sold as juveniles when they’re only a couple of inches big, tricking unknowing hobbyists about their true care requirements.

The truth is that Oscars are monster fish that not many hobbyists have the ability to care for. However, if you’re willing to give a very large tank to one single fish, then the oscar fish might be the best choice.

Their Natural Habitat

Oscar fish are scientifically known as Astronotus ocellatus. They are a type of cichlid though they’re not as aggressive as some of their closest relatives.

Instead, these gentle giants scour the basin of the Amazon River basin in South America for whatever can fit in their mouths. They have been documented in most countries throughout South America, but have known established populations in the United States as well as Singapore.

These ecosystems are heavily forested with a silt substrate. They prefer slow-moving rivers and tributaries with various structures, like tree limbs, where they can hide and claim territory. Oscars can be found living solitary lives or in small groups.

Oscar Fish

Tank Requirements

In terms of fishkeeping, oscar fish are just another type of South American fish from blackwater conditions. However, their mature size is what makes them difficult to keep.

Most oscar fish will surpass 1 foot in length at their mature size. In the store, they’re usually sold while they’re still small, which makes more hobbyists willing to buy them; this is a mistake as they’re put into a holding tank that they’ll grow out of with a promised upgrade in the near future. Most times, they’ve never actually given a bigger tank after that and the fish needs to be rehomed.

The bare minimum tank size for any type of oscar fish is 75 gallons. A 125 gallon tank is even better to allow for more swimming space and more controllable water parameters.

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This tank should be given a powerful filter to keep up with the messy habits of oscar fish. Additional flow is not needed and lighting can remain dim. They prefer a sandy bottom and will enjoy rummaging through it for additional food to eat; this also means that live plants are not safe from being uprooted!

Otherwise, oscar fish tank setup is simple. Add some rocks and driftwood for shelter and your oscar will thrive.

What Is The Biggest Type?

We mentioned before that oscars are monster fish and can easily surpass a foot at adult size. But how big can they actually get and are the different types of oscar fish different sizes?

The biggest that oscar fish can get to be in captivity is about 18 inches and several pounds. It is rare for them to get any bigger than this, though they can keep growing over their 20 year lifespan.

Most types of tiger oscar that were derived from Astronotus ocellatus have the ability to reach these monstrous sizes. Some breeders have made short-bodied varieties that may stay slightly smaller, though


If oscar fish are known for one thing, it’s their personalities. These fish are full of life and will let you know when they don’t like something in their tank.

It is important to understand that Oscars are not aggressive fish, though most hobbyists refer to them as aggressive. Yes, they will defend their territories and chase after problematic tank mates, but they won’t attack other fish without a reason. Instead, they are labeled as being aggressive due to their appetite which makes them eat almost everything in sight.

Oscars are slow-moving fish. They will usually be seen floating in the water column, occasionally moving around to search for food. That being said, they enjoy having plenty of swimming room for when they get quick bursts of energy.

At the same time, these fish can be quite temperamental. If something is added to the tank that they don’t like, they will become less active and might even try to uproot whatever the new addition is. Even then, they are likely to uproot decorations with no intent.

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Lastly, oscar fish love their owners. They will recognize the person that feeds them and may eat directly out of their hand.

Tank Mates

Due to tank size and waste management, most hobbyists don’t keep their oscars with other fish, especially not in a community tank. If space isn’t a problem, then there are a few tank mate options that can go with most types of oscar fish.

The goal is to get a fish that is too large to be eaten. Some hobbyist feel getting small, fast, schooling fish that can escape your oscar in a large tank are worth it. The logic here is that they can be easily replaced. Going with small fast fish is an approach I wouldn’t recommend.

One of the best oscar fish pairings is with the severum cichlid (Heros severus). This is because these fish share similar tank and water conditions. Severums are also big enough to hold their own against a full-grown oscar.

Other possible oscar tank mates include:

  • Chocolate/emerald cichlids (Hypselecara temporalis)
  • True parrot cichlids (Hoplarchus psittacus)
  • Green terror cichlids (Andinoacara rivulatus)
  • Flagtail prochilodus (Semaprochilodus insignis)
  • Silver dollars (Metynnis spp.)


Oscars may be the least picky of all eaters; oscar fish eat anything that fits inside their mouths, and we mean anything.

Oscar fish are primarily carnivores, meaning they prefer a diet that consists of meaty foods. From there, the possibilities are nearly endless for food options.

These beautiful fish will enjoy a variety of live, frozen, and freeze-dried foods such as:

  • Worms (bloodworms, ,blackworms, earthworms, Tubifex worms)
  • Shrimp (full raw shrimp, brine shrimp)
  • Mollusks (clams, scallops, mussels)
  • Insects (insect larvae, crickets, mealworms)

To help keep costs down, oscar fish may be given high-quality cichlid flakes or pellets; pellets may be preferred as some oscars may refuse to come to the surface to eat. Most local pet stores also carry specific oscar fish food.

These large fish will eat as much food as they’re given, which can lead to water quality issues and a lazy fish if overindulged. Eventually, your fish will greet you at the top of the tank waiting to be fed.

Oscar Fish

Above is information about How big does an Oscar Fish get? Introduction to Oscar Fish that we have compiled. Hopefully, through the above content, you have a more detailed understanding of Oscar Fish. Thank you for reading our post.

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