The Ultimate Oscar Fish Guide: Care, Diet, Setup & Breeding

Oscar fish are a widely popular freshwater cichlid species. They achieve very large sizes and are extremely interactive; basically, a freshwater puppy dog! They come in a variety of colors and patterns, so there is one out there for everyone.

This complete guide will cover everything you need to know about keeping, caring for, and breeding the Oscar Cichlid. These fish make incredible pets, so let’s get started!

oscar fish

About Oscar Cichlids

  • Scientific Name: Astronotus
  • Temperament: Moderately Aggressive
  • Care Level: Easy
  • Origin: South America
  • Common Names: Marble Cichlid, Velvet Cichlid


Oscar Cichlids are often given a very bad rap as an overly aggressive fish. This isn’t entirely true; Oscars simply try to eat any fish smaller than themselves, but this behavior is displayed in most fish, including platies, mollies, and goldfish.

The issue arises because Oscar get much larger than other fish, so they can eat most other commonly available freshwater fish. If given enough space, generally 125 to 150 gallons, two Oscars will get along swimmingly.

Each Oscar cichlid has a unique personality, just like any other pet. They are interactive, and if you do keep two, you will be able to see just how much personality each fish has. It’s amazing to see the differences and interactions between two fish of the same species!

Natural Habitat

Oscar Cichlids come from the Amazon River, primarily sluggish moving areas that are extremely warm. Oscars do not tolerate cold water at all, and temperature is one of the main restrictions of their habitat.


Oscars typically live at least 10 years, and some can reach 18-20 years, though 10-12 years is much more common.


Oscars can reach absolutely massive sizes in the wild, but in captivity they often stay between 10-14 inches. There have been recorded cases of Oscars reaching 16-18 inches as well, but those sizes are rare.

oscar care

Oscar Fish Care

Here are some essential things you should learn before attempting to keep Oscars:

Basic Setup Requirements

While Oscars require large tanks, they are extremely hardy fish and are easy to care for. Most tank mates should be avoided, but an Oscar’s personality can easily fill the empty space.

  • Tank Size: Many sources recommend a 55-gallon tank for Oscars, but this does not give them enough room to turn around. A 75-gallon can work for smaller Oscars but is still a bit of a tight squeeze. A 125-gallon or 150-gallon would be ideal for these fish and is large enough to house two of them.
  • Water Flow: Oscars come from slow moving rivers, but they are not picky when it comes to flow rate. They will be fine in low, moderate, and high flow rates, and can often be seen playing in the output flow.

Aquarium Water Parameters

The Oscar Cichlid comes from a softer, low pH area of the Amazon River, but these hardy fish are highly adaptable. Even though they can survive in most water, they do prefer softer, more acidic water.

Basic guidelines for Oscar water parameters:

  • pH: 6.0-7.5
  • Temperature: 77-80°F
  • Alkalinity: 8°-15° dGH

When keeping Oscars, stability is more important than ideal parameters. If your hardness is a bit off, it’s better for the fish to adjust to your water, rather than the parameters changing frequently.

Changes to water hardness, pH, and temperature cause stress to your fish, which can shorten its lifespan.

Oscars, like all fish, are sensitive to ammonia and nitrite, and nitrates. Ammonia and nitrites are extremely toxic and should not be present in the tank at all. Be sure to properly cycle your aquarium before adding an Oscar Cichlid, or any other fish.

Nitrates tend to be more of a problem for Oscar keepers. They build up in the aquarium over time in clean, properly cycled aquariums.

Since Oscars are huge waste producers, most owners change their water once or twice every week. Failing to keep nitrates below 40ppm lowers the Oscar’s immune system, and often leads to Hole-In-the-Head Disease, or HITH.

It is extremely important to test your water, and the API freshwater master test kit is the most accurate test kit on the market, and cheapest per test.

Feeding Your Oscar the Right Diet

Every fish should be fed multiple types of food per week. Oscars are primarily carnivorous, so their diet should be meat based. They need a staple commercial pellet, since these provide necessary minerals and vitamins.

Hikari Cichlid Gold is a good staple pellet for Oscars, and other carnivorous cichlids. They can also be fed beef heart, earthworms, night crawlers, jumbo krill, frozen brine shrimp, and freeze-dried crickets, grasshoppers, mealworms and bloodworms.

Some of these foods, such as bloodworms and beef heart, are extremely fatty and should only be fed 1-2 times a week. Live food such as feeder fish are also acceptable, but avoid feeder goldfish, as they contain too much Vitamin A, which can be harmful to Oscars.

Overfeeding your fish can lead to bloating problems and excess ammonia, nitrite, and nitrate, so it is important not to overfeed your fish. Feed your fish only what they can eat in 15-30 seconds one to two times a day, unless you are feeding live food that must be hunted down.


Oscar cichlids do not school, but if provided with a large enough tank, they will coexist peacefully with others of their species.

oscar species

Types of Oscar Cichlids

There are three main species of Oscar Cichlid, but only one is commonly kept. This commonly kept species has over twenty different color morphs, and no one can resist all these colors!


This is the most popular type of Oscar, and these are the ones you see in stores. They come in a massive variety of color morphs, including the Tiger Oscar, Albino Tiger Oscar, Albino Oscar, Red Oscar, Albino Red Oscar, Golden Oscar, Super Red Oscar, and Lemon Oscar. There is also a Blueberry Oscar, but these are a product of dyed fish, which can result in a mortality rate over 90%, and the color will fade after a year. These are the Oscars known for their patterns and personalities.

  • Scientific Name: Astronotus ocellatus
  • Size: 10-16”
  • pH: 6.0-7.5
  • Temperature: 77-80°F

Fat Oscar

These Oscars are extremely rare in the aquarium trade and are often mistaken for their more popular cousin, Astronotus ocellatus. These fish also produce an extreme amount of waste, so even though they are smaller, they require just as much filtration. They are also extremely hardy and will eat the same food as other Oscars. Even though little is known about this species, they thrive under the same conditions as the common Oscar.

  • Scientific Name: Astronotus crassipinnis
  • Size: 10″
  • pH: 6.0-8.0
  • Temperature: 77-80F

Bumble Bee Oscar

This is another rare Oscar species, though not as rare as the Fat Oscar. These Oscars are gorgeous, black with yellow stripes, hence their bumblebee name. They also have a large red “eye” just before their tail, which is a shockingly bright color. Their care is the same as the other Oscars and they can be kept with others of their species.

  • Scientific Name: Astronotus orbicularis
  • Size: 10-16″
  • pH: 6.0-7.5
  • Temperature: 77-80°F

Oscar Tank Mates

When choosing tank mates for your Oscar, keep in mind that they will eat any fish smaller than them when full grown. Also, due to their aggressive nature, tank mates should be added to the tank before, or at the same time that the Oscar is.

oscar tank mates

Suitable Tank Mates

  • Other Oscars
  • Sailfin Pleco
  • Common Pleco
  • Green Terror Cichlid
  • Jack Dempsey Cichlid
  • Other large Cichlids

Tank Mates to Avoid

Here are a few species you should not keep with your Oscar:

  • Small Fish: Any fish that has a maximum size below 10” will become a snack as your Oscar grows.
  • Invertebrates: Shrimp, snails, and crayfish will be eaten by your Oscar. Some Oscar keepers breed the self-cloning crayfish in order to add some variety to their pet’s diet, and others feed excess livebearer fry.

Setting up an Oscar Tank

If you’re looking to set up an Oscar only tank, then this section is for you!


  • Tank: The best tank size to start off with is a 125-gallon tank. This allows your Oscar enough room to swim around and turn and allows the option to add tank mates in the future. Larger tanks are easier to begin with, since their waste is diluted, and nitrates will build up slower than in a smaller tank.
  • Filtration: For the large tank size that Oscars require, canister filters are the best option. These will keep large tanks crystal clear and can keep up with the massive amount of waste produced by Oscar Cichlids.
  • Heater: A heater is essential to keeping Oscars, because cold temperatures, even room temperature, can be a death sentence.
  • Lighting: This is a personal choice, since Oscars do not have much of a preference when it comes to light. Additionally, cichlids in general love to uproot and tear apart plants, so lighting is not needed for plants, as they often do not survive.

Choosing a Substrate

Oscar Cichlids will sometimes root around in the substrate to make sure they get every last morsel of their food.

If their substrate is gravel, they can swallow small pieces of gravel (which includes all gravel when you have a 16” fish!). The gravel can become impacted in their intestines and become a serious health risk.

The best substrate for these fish is a sand substrate. Sand can easily pass through their digestive tract and does not pose the same risks as gravel.

One thing to be aware of when housing fish on a sand substrate; if they eat the sand, their feces are often white and stringy, which can be confused with internal parasites.

Oscar Cichlids in a sand-substrate tank

Aside from sand, some people use plain tile as a substrate, which is easy to clean around and more appealing than bare bottom tanks, which is the last option. B

are bottom tanks are extremely easy to clean, which is a big plus when it comes to messy fish like Oscars, but it is not the most aesthetic option.

Adding Live Plants

Live plants and Oscars do not mix, as Oscars love to destroy them. It is nearly impossible to get plants to thrive when surrounded by these fish. Alas, if only we could combine the stunning Oscar and beautiful planted tanks!

Rocks and driftwood can still be used as hardscape, though Oscars may move smaller rocks and light driftwood around.

Cycling Your Aquarium

Oscars are extremely sensitive to ammonia and nitrite, so it is essential to cycle your aquarium before introducing any fish. Even though you must wait to add fish, there is no need to wait to add the hardscape. This is your time to set up the aquarium exactly to your liking before adding fish.

This essential cycling time not only allows you to set up your perfect hardscape, but it also allows you to research everything you need to know about your planned pet. Additionally, it allows other types of bacteria and biofilm to establish, which leads to an overall healthier tank.

Breeding Oscars

After keeping Oscars and experiencing their personalities, some owners want to take their love for Oscars to the next level by breeding them. Some owners who keep a pair of Oscars may simply come home and find that they own a perfect sex ratio.

breeding oscars

The Breeding Setup

Breeding Oscars can be a daunting task, despite the fact that they are beginner fish. Startup costs can be high because of the tanks and materials needed.

Oscars can have up to 3,000 fry in one spawn, which will require hundreds of dollars’ worth of tanks, heaters, filters, air pumps, manual labor, and other equipment.

Once a pair bonds, there isn’t much that will stop them from spawning. This is not meant to discourage anyone from breeding these magnificent fish, it is only a warning.

  • Strategy #1 – Dedicated Breeding Tank: Setting up a tank aside from the “main” or “display” tank is the first option. This includes getting a new tank, heater, and sponge filter(s) depending on the tank size. These need to be purchased either way, since a large adult female Oscar can lay 3,000 eggs, and multiple grow out tanks will be necessary. In this case, instead of removing the fry from the tank, the adults will be removed instead. This option is more commonly used when the adults are separated from one another, either for conditioning or other reasons.
  • Strategy #2 – Dedicated Fry Tank: Since Oscars are commonly kept in male/female pairs in the main tank, it may be easiest for most to simply add in a flat breeding surface, condition them, raise the temperature, and wait. Once the fry are grown enough to be moved to a fry tank, they can simply be siphoned out, which is the most common practice. This is also the circumstance for accidental breeding, which occurs when someone purchases two Oscars as companions and they end up forming a bonded breeding pair.

The second option is the one most commonly chosen for Oscars, since they generally don’t have tank mates that will stress the pair or damage the eggs. Additionally, it is less stressful for the parents since they are not being moved from tank to tank.

Setting up a Fry Tank

Fry tanks, especially for waste producers like Oscars, are typically bare bottom for ease of cleaning. They need a heater to keep the water between 77 and 80 degrees and a sponge filter to keep the tank cycled.

The sponge filter is the safest filter for fry, as other filters, such as hang-on-back and canister filters, can suck fry into the filter and grind them up in the impeller or coarse sponge. Sponge filters also keep particles of food that the fish miss within reach, so you will probably observe several fry pecking at the sponge filter 24/7.

Fry will die if there is any ammonia or nitrite present, and they are more susceptible to nitrate poisoning than the adults, so the nitrates should never go over 10ppm in the fry tank. Aside from this, the parameters of the adult tank and fry tank should be identical.

The size of the grow-out tank will vary depending size of the spawn, which can be between 50-3000 fry. Tanks between 20 gallons and 150 gallons are often used, though some standby tanks are needed as fry grow.

Oscar fry tend to grow at different rates. As a result, smaller fry might need to be kept in a separate tank to avoid becoming a snack for the larger fry.

This is another bonus to keeping all of your tanks with identical parameters; no acclimation is needed for the fry, which makes moving them one hundred times easier!

Determining Gender

The only way to determine the gender of your Oscars is the breeding tubes, which only appear right before and during spawning. The females have a stubby breeding tube that is flat at the end and very wide. The males have a thin breeding tube that is pointed at the end.

Sexing Oscars is very similar to sexing angelfish, which more people have experience with. Since the tubes are only seen during the spawning process, it will be nearly impossible to go to a store and purchase one male and one female Oscar, especially if they are juveniles.

oscar cichlid pair
Ashish Ghosh [CC BY 3.0], from Wikimedia Commons
Buying a proven breeding pair is often cheaper than trying to produce a pair yourself. Oscars take at least 14 months to reach sexual maturity, but some young Oscars will refuse to breed for the first three or four years of their lives.

When taking into account the amount of food and time you would have to put into raising multiple juveniles, the proven pair is often the less expensive option.

Conditioning Your Fish

The typical conditioning period for fish is 1-2 weeks. Best results are achieved using live food such as feeder fish (guppies, rosy red minnows, and other livebearers provide the most nutrition), earthworms, shrimp, snails, and frozen food grade shrimp and fish.

During this period, the male and female should be separated, fed 3-5 times daily, then introduced to one another in the breeding tank. However, it is possible to keep the parents together during this period without separation. The female should be fed more heavily than the male in order to promote proper egg development.

Inducing Spawning

The temperature should be raised between 82- and 85-degrees Fahrenheit in order to trigger spawning behavior. The parents will need some kind of flat surface to lay eggs on, and flat tiles or slate slabs are often used. Their colors will intensify, and their breeding tubes will drop right before they spawn.

Caring for the Eggs

Both parents will vigorously guard the eggs from potential predators, and unfortunately, that includes you. Avoid checking on them too regularly, as they may feel threatened and eat the eggs/fry. The female will fan the eggs to prevent fungus growth, as well as remove the unfertilized eggs by eating them.

Fry Care

Around 4 to 7 days after laying the eggs, the adult Oscars will build a pit in the substrate and move the fry there. It takes around 10 or more days after being laid for the fry to truly become free swimming.

At this stage, the fry can be removed by siphoning them into a bucket and transporting them to a different tank with the exact same water parameters.

At this point, the fry can be fed baby brine shrimp, which are easy and cheap to hatch. They can be fed these alone for the first 1-2 weeks, but other food should still be added.

Blackworms and white worms are a good addition between weeks 1 and 3, depending on how fast the fry are growing. After the third week, the fry should accept ground up flake food and powdered fry food.

Large fry will eat smaller fry, so it is important to move the larger fry to a larger grow out tank. Before you get worried about a never-ending amount of tanks, Oscar fry can be sold at a small size, as small as 1”.

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