Oscar Fish – Care Guide, Breed Profile, Tank Setup, Diet and Breeding

Oscar fish are one of the most popular species to be kept in home aquariums. If you’ve ever been into an aquatic pet center, you would have certainly seen them available for sale.

They are an active and vibrant choice. They’re also hardy, although oscar fish care should be thoroughly researched for those new to fishkeeping because the care for them can be somewhat complicated.

Close up of an oscar fish against a blurred background
© Dmytro Synelnychenko – stock.adobe.com

In this article, we aim to tell you all you need to know on how to keep and look after your oscar fish, to help you get enjoyment out of them for years to come.

We’ll cover the breed profile, basic facts and statistics, temperament, habitat, tank requirements and more. We will also discuss what’s best to feed them, and how to buy and breed them.

By the end of this article, you should be fully prepared and ready to go buy your first oscar fish to add to your home aquarium.

Overview and Statistics

Let’s get started with some of the most important facts about thei care requirements.

The below table lays out some of the key characteristics of the breed, as well as important information about their appearance and upkeep. If you’re short on time, you should find the information you are looking for here.

Common name(s):Marble/velvet cichlid, tiger oscar, red oscar, albino oscar, zebra oscar
Scientific Name(s):Astronotus ocellatus
Origin:Amazon, South America
Care Level:Difficult
Adult Size:12 inches
Color Form:Black/orange/red
Lifespan:10 to 13 years
Minimum Tank Size:70 gallons
Typical Tank Setup:Deep sand bottom. Scattered rocks with floating plants
Tank Level:Bottom dweller
Water Conditions:Freshwater. 72-77° F, KH 5-19, pH 6.0-8.0
Tank mates / Compatibility:Large or spiny fish including jack dempsey, bala shark, silver dollar, pleco. Smaller fish will likely be eaten.

As is clear from the above table, good oscar fish care is not easy for novice keepers, as they do have some behavioral quirks.

They originate from Central and South America and have a relatively long lifespan in captivity.

In home aquariums, they are popular with fish keepers of intermediate or higher experience. They are a common choice for aquatic hobbyists that are looking to move from starter breeds to something a little more challenging.

What do Oscar Fish Look Like?

Most tend to have the same kind of appearance, save some color variations. The tiger oscar has a blue-black base color, with a red-orange pattern on the sides of the body. The pattern is similar to the mottled black seen on a jaguar and is very striking to the eye.

Other variations include the zebra (black/white), red (orange/red) and albino. Albino oscar fish are the same shape but are creamy white with splashes of orange/red scattered along the body.

They have long, slender pelvic fins and long dorsal fins which have a spiny appearance. The dorsal fins stretch the length of the back before almost joining the upper caudal fin lobe. On the dorsal fin, there is often an eyespot in a bright color.

They have a set of teeth, but these are concealed in the very back of the mouth. They also have some pharyngeal teeth in their throats.

Their eyes are relatively large compared to body size. They have a docile and friendly appearance. The gills are not very prominent, in fact in some colorations, they are well camouflaged.

Oscar fish can grow to between eight and 16 inches, although they are most often towards the lower end of the scale.

Because of these colors and patterns, they’re very attractive, which helps explain their growth in popularity as pets. They can change color as they age, gradually becoming more vibrant and displaying extra colors in various places on their bodies.

In terms of telling male versus female, this can be incredibly difficult to do, as they’re one of the few species that are almost identical in size and shape, regardless of sex.

The only way you may be able to tell, is to look for a small cone-shaped protrusion located around the anal opening, which may help you to establish the fish as a male.

Natural Behavior and Temperament

They aren’t known for being the friendliest fish you can buy, but still, they’re not the worst offenders. They can be kept with most other species of a similar size and, if left to their own devices, there shouldn’t be any issues.

However, they can be quite territorial, especially if they’re breeding. It’s worth mentioning that females normally lay their eggs on flat rocks. Because of this, they tend to claim territory near the bottom of the tank, defending their patch of substrate and rock.

When they do attack, they’ll take small bites out of other fish, but they usually only do this when they feel those fish are trespassing on their territory. They generally prefer having space to themselves, calmly bimbling about, investigating their surroundings.

They also like to hide among plants and behind rocks if they need some peace and quiet. This type of behavior may become amplified if they’re kept in crowded conditions.

Oscar fish can also be playful and inquisitive with their owners. They are usually very interested in what is going on around them outside the tank.

They are known to be jumpers, frequently leaping out of the water. Therefore, you should make sure you have a secure lid. Otherwise, you may find your new pet on the carpet.

They also like to root about in the substrate and rearrange their environment. Therefore, be prepared for them to make quite a mess in your aquarium.

Habitat and Tank Requirements

They are native to most of the Amazon River basin, meaning that they’re used to living in warmer, tropical freshwater. Therefore, you may need to adapt your aquarium to ensure the best oscar fish care.

What Size Tank do They Need?

If you only have one, then your tank size should be at least 70 gallons. To accommodate a pair, you’ll need a tank of 100 gallons or more.

Water Type and Parameters

Most types need water in the temperature range of between 72 and 77 degrees Fahrenheit, or 79 to 86 degrees for breeding. The water also needs to be clear, tropical freshwater, as it’s what they’re used to in their natural environment.

What Substrate Should I Use?

They need their tanks to have a deep sand base, as well as a number of rocks decorating the bottom. This replicates their natural environment, and is especially true in the case of breeding pairs, as it is where the females will lay their eggs.

Filtration Requirements and Water Flow

Since they’re used to the wild flowing water of the Amazon River basin, they don’t mind a reasonable amount of water flow in the tank. On top of that, they also need their water to be as clean and clear as possible.

This means that a strong filtration set up that creates a medium flow of water and currents in the water would be ideal for them.

Lighting Requirements

Oscar fish don’t seem to have too much of a preference regarding lighting. They’re happiest with natural daylight cycles, without any extremes.

So, as long as the tank isn’t too bright at night, or too dark during daytime hours, mostly mimicking a natural day/night cycle, then they’ll be happy.

Plants and Decorations

It should be noted that if there are plants in the sand, they could be ripped out by your oscar fish. They frequently do this in the wild, to uproot and disturb any small edible creatures which are hiding among the roots.

However, if you do want plants decorating the aquarium, then floating plants would be a great compromise, as they generally leave these alone.

They like to have lots of areas to investigate and forage. So, scattered and stacked rocks are also welcome. That said, they need to have enough open space to swim, too.

How Many Oscar Fish Can You Have Per Gallon?

A community of oscar fish, exploring a planted tank
© ake – stock.adobe.com

As mentioned above, a 70-gallon tank is the minimum recommended size for one individual. If you have a 100-gallon tank or bigger, this is sufficient for a pair, but no more, because they are too territorial.

Oscar Fish Diet

They are naturally carnivorous, but not overly fussy and easy to feed. In this section, we examine the ins and outs of feeding and diet.

What do They Eat in the Wild?

In the wild, othey normally have a diet of crustaceans and small insects, as well as worms. They readily pluck insects from the water’s surface, as well as rooting around in the substrate for morsels.

What Can You Feed Them at Home?

Ideally, in a home aquarium they will be fed insects, mealworms, and crustaceans.

However, their diet should also consist of a quality pellet, which gives them the necessary proteins, vitamins, and plant/algae that they would find in their natural habitat.

What Kind of Human Food Can They Eat?

Generally speaking, they should avoid most human foods, as a lot of what we eat can be high in fat and salt, especially for a fish. This could end up promoting disease, which is why it’s best avoided.

However, they can be fed some foods that we eat, such as frozen peas, although these will be more of an occasional treat than a daily food source. Make sure they’re shelled and chopped into small pieces before feeding.

How Often Should You Feed Them?

This depends on their size. They tend to be incredibly hungry on an almost constant basis, meaning that they will eat anytime food is put in front of them.

However, you should avoid overfeeding them and keep feeding to twice a day. Let them eat as much as they want, but remove any uneaten food after about three minutes.

Any Special Care Requirements

Aside from what we’ve already mentioned above, there aren’t any special care requirements. So long as their tank and dietary requirements are followed, they are very resilient.

That said, they must eat a balanced diet, as they can fall ill if they become deficient in vitamin C. Standard flaked fish foods will be nutritionally dense enough to avoid any potential deficiencies.

Compatibility Between Oscars and Other Fish

Oscars will readily eat smaller fish, so they should only be housed with other large species. Good choices for tank mates could be green terrors, large armored sailfin plecos and jaguar cichlids.

Other than this, it’s mainly down to how territorial they can be that leads them to attack other fish. This can vary between individuals, but as long as the tank doesn’t become overcrowded, you shouldn’t have any issues.

How Many Oscar Fish Can You Keep Together?

This is dependent on how large the tank is, as covered above. They aren’t a community fish, and multiple males can present territorial problems.

It’s best to keep a number of females together with one male, or solely females if you’re not interested in breeding.

Buying Oscar Fish

When you’re buying an oscar, you need to look out for any skin damage or unusual marks that it might have. Clouded eyes, ragged fins or scale loss are signs of disease. In terms of age, you’re better off buying younger individuals, so they have a good chance of adapting to your tank more quickly, as juveniles are more able to do.

If you want to buy one from online, you should also do some research on the seller beforehand, to ensure that you’re getting what’s advertised. However, they are widely available for purchase online, and they do ship well.

How To Breed Them

Breeding oscars is more challenging than many other fish, as they can be quite difficult to pair with each other. Because of that, it’s worth buying a pair that are already paired and breeding. Once they’re paired, it can be fairly easy to breed them if you’ve got your tank set up right.

To encourage oscar fish breeding, you’ll need to keep the tank’s water as clean as possible, changing 20-30 percent of the water twice a week. Their diet should also be varied, but consistnt when it comes to timings on when tthey are fed. The water temperature should be between 79 and 86 degrees Fahrenheit.

You also need to make sure you have plenty of rocks embedded in the sand. This is so they can safely lay their eggs.

You will know they’ve begun breeding when you start noticing changes in their habits, such as swimming differently and seemingly playing with each other. After that, the female should lay up to 1,000 eggs over the following days, around 100 at a time.

Their eggs should hatch after about three days, and appear opaque when first laid, but become transparent in the following 24 hours. Oscar fish are protective parents and will closely guard their young when hatched.

The fry may also hang on to their parents once they have begun to swim. However, to ensure survival of the fry, it may be best to separate them once they reach about an inch long, as the adults may become aggressive and consume them.

Interesting Facts and Trivia

  • They are close relatives of piranhas.
  • They are almost dog-like in the way they behave with their keepers. In fact, they are sometimes called “water dog” because they appear to wag their tails when their keeper comes near. They will even eat from your hand.
  • Some people become so attached to their oscar fish that they take them to a taxidermist after they have died, so they can keep them forever.
  • They often have their own ideas about how their aquarium is laid out. You may notice they take it upon themselves to do their own redecorating, moving objects around and doing some landscaping.

Frequently Asked Questions

Do Oscar Fish Have Teeth?

They do have teeth, although they’re pretty small and can’t do much damage to people or larger fish.

Normally, a bite will just result in a small scratch. But they aren’t as harmless to smaller fish, eating any small enough to fit in their mouth.

Do Oscar Fish Sleep?

Fish don’t sleep the same way people do, and oscars are no exception. They enter into what could be called an “energy-saving state,” but they keep moving during this state, which makes it seem like they’re not sleeping.

What do Baby Oscar Fish Eat?

They normally eat the same as their more mature counterparts, although they’ll obviously need less.

The likes of mealworms and pellets that are high in vitamins and proteins are perfect, but you can also feed bloodworms too. They are greedy, so try to avoid overfeeding them.

How Fast do Oscar Fish Grow?

They generally grow at a rate of an inch per month for the first year of their lives. However, if you’ve got a smaller tank, they will stop growing once they’ve reached a size compatible with their environment.


Oscar fish won’t be the best choice if you’re just starting out as a fish keeper.

Because of their temperament and breeding habits, they can be more difficult for beginner fish keepers to handle and care for properly. For example, they can be aggressive and territorial, so you need to be conscious of which other species are kept alongside.

You’ll also need quite a large tank, 100 gallons for a pair of oscars, and constant water flow which mimics their home environment to keep them happy and comfortable.

However, if you have a little more experience, this beautiful species can make rewarding pets. Their diet is fairly simple, and so long as you are familiar with tank care and filtration setups, this species can be a wonderful and entertaining addition to your home aquarium.

Is there anything you think we missed about the oscar fish? Have any tips for someone considering buying one? Please do let us know in the comments below.

Happy fish keeping!

Wendy Kathryn

Hi, I'm Wendy, the owner and creator of this website, an experienced fish keeper and avid student of the art since 2010. My aim is to help beginners avoid the many possible mistakes when getting started in this wonderful hobby.

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