Red Oscars (Astronotus Ocellatus) 101: Complete Care Guide (2024)

Featured Image - PT-0066 - red oscars
Featured Image – PT-0066 – red oscars
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: April 6, 2024
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Oscars can make interesting and enticing pets, but too often their care needs are overlooked. The maintenance and effort required for these species can be relatively intense, so it’s important to conduct ample research prior to deciding to house them. If you’re considering whether the red oscar fish or any other variety is right for you, take a look at this exhaustive guide on their care.

Article Summary

  • Red Oscars are a type of freshwater fish belonging to the Cichlidae family, known for their aggressive temperament.
  • Oscars are not overly sensitive to water chemistry but can suffer if water quality deteriorates, so regular water changes and good filtration are essential.
  • Oscars are not ideal for beginners due to their territorial nature, large size, and specific care requirements.


Most cichlids like the popular kribensis, are from either Africa or South America. The oscar fish originates from the latter, though it has been found in other areas of the world since its introduction to the fishkeeping hobby.

Oscars are native to Brazil, Columbia, Peru, Ecuador, and French Guiana. They are mostly found in the Amazon River basin.

Natural Habitat

Wild Oscars live in still, moderately shallow waters – particularly if the bottoms are sandy, muddy, smooth, or soft.

Some of their common natural habitats include swamps, marshes, ponds, floodplains, and canals.

Physical Appearance

Red Cichlid in an Aquarium
Red Cichlid in an Aquarium

The oscar fish can be easily identified by its long and oval body shape.

Its dorsal fin and anal fins span along its body to the caudal fins, which creates a fan at the bottom.

Wild specimens and tiger Oscars are covered in a range of orange and black splodges, but these colors can change gradually.

The majority of varieties have been made through selective breeding, including the green oscar, lemon oscar, and blue oscar.

How Do You Tell If They Are Male or Female?

Oscar fish are difficult to sex as they are monomorphic. This means that there is very little external difference between genders.

However, a process called venting can help you figure out whether your oscar fish is male or female. This involves catching the fish in a net and flipping it over (while still submerged) so you can see its genitals.

Examine the color, size, and shape of the holes.

In female oscar fish, one hole will be larger than the other. This larger hole is the egg tube.

In male oscar fish, both holes will be the same size.

The color around the region will also be slightly darker than in females.


Make sure you take care when handling your fish during the venting process to avoid injury and stress.

Red Oscar

Red Oscars also known as Velvet Cichlid/Marble Cichlid can be distinguished by their gorgeous two-colored appearance. Their body is a stunning combination of black and bright red. Both of these colors blend around their back, resulting in a truly beautiful transition.

The fins on a red oscar fish are normally black. Their eyes have an orange rim and stick out slightly above their head.

Tiger Oscar

Tiger Oscars are one of the most popular varieties kept in aquariums. They are incredibly beautiful with black and orange splotches on their skin that resembles the markings on a tiger.

This pattern is typically towards the end of the tail, but it can also cover the entire body. Their base coloration is black with a vivid red or orange pattern. Some specimens have dark bands near the rear, too.

Albino Oscar

As you have probably already guessed, albino Oscars are almost completely white, other than an orange/red lattice pattern. This pattern is typically towards the rear.

Some specimens have more intense coloring (without any mixed colors) on their pattern than others, which increases their value.

Black Oscar

Compared to other varieties of oscar fish, Black Oscars are a little less exciting in appearance. Their base coloration is black with light bands that span the length of their body.

Some individuals also have a light-colored belly.

Black Oscars have black fins and an orange rim around their eyes.

Blue Oscar

The Blue Oscar is a very pretty crossbred variation. Its whole body is painted in contrasting hues of blue, alongside a yellow or blue pattern.

Their scales also have a deep blue lining, which adds to their beauty.

How Big Do Oscars Grow?

Most Oscars grow to around 12 inches in size, so They are not small fish. Some specimens have been reported to reach up to 18 inches in length!

Aquarium Varieties

Oscar fish come in an assortment of colors, all of which can look breathtaking in a fish tank. Here are some of the most common varieties of oscar fish you will come across in the aquarium hobby.

  • Red Oscar (Astronotus Ocellatus)
  • Tiger Oscar (Astronotus Ocellatus)
  • Albino Oscar (Astronotus Ocellatus)
  • Black Oscar (Astronotus Ocellatus)
  • Blue Oscar (Astronotus Ocellatus)
  • White Oscar (Astronotus Ocellatus)
  • Florida Oscar (Astronotus Ocellatus)
  • Veil Tail Oscar (Astronotus Ocellatus)
  • Green Oscar (Astronotus Ocellatus)
  • Lemon Oscar (Astronotus Ocellatus)
  • Wild Oscar (Astronotus Ocellatus)

I like red Oscars and tiger Oscars as their colors, and patterns are stunning. That said, any variety of oscar is a great centrepiece fish for your tank.

Do Oscars Make Good Pets?

Oscars can make good pets as long as you have got the time to look after them properly. They are an interactive and intelligent species, just like any other type of cichlid.

However, their care needs are a bit more complex than some other cichlid species, so they require a fair amount of work and maintenance to keep happy.

Can You Raise Them in Captivity?

Red Oscar at the Bottom of a Fish Tank
Red Oscar at the Bottom of a Fish Tank

Unlike other cichlids, Oscars are quite hard to breed in captivity.

This is mostly down to their pickiness when choosing a mate to spawn with.

Are They Good for Beginners?

Oscars are not the best fish for beginners for several reasons. For one, they are highly territorial, which means they can be problematic when kept in community tanks.

Secondly, they grow to a large size and require a tank that can accommodate their adult length.

Thirdly, Oscars require a clean environment as they are prone to a few illnesses and diseases like hole in the head disease. As this fish requires a lot of care, They are better suited to experienced aquarists.


If you are new to keeping fish and have your heart set on a cichlid fish, then there are plenty of other species in this family that are a better choice.

For example, the convict cichlid is a fantastic beginner fish as it is hardy, easy to feed, and straightforward to breed.

How Long Do They Live For?

Oscar fish typically live for around 10 years, though some sources claim that they can live for up to 20 years if cared for exceptionally well.

As you can see, these fish are quite the commitment and are not the sort of pet you should buy on a whim.

If you want to own an oscar fish, make sure you are able to look after them for the entirety of their life. Compared to other freshwater fish species, Oscars take a considerable amount of work and energy to keep healthy.

Do They Die Easily?

For the most part, oscar fish are relatively hardy. Unlike other cichlids like discus, Oscars are easy to feed and are not overly sensitive to water chemistry. However, like all fish, they can quickly decline if their environment is dirty or is high in ammonia, nitrite, and nitrate.

These fish are not picky eaters and are relatively easy to feed in the aquarium…

They will eat practically anything you offer them.

Oscar fish are omnivores, which means they eat meat-based foods and plant matter. Wild Oscars consume small fish, larvae, insects, crustaceans, and bits of plant debris.

What To Feed Red Oscars

You can feed them pellets or flake food that is targeted for omnivorous fish. Some brands are even designed especially for cichlids, which is ideal. Alongside commercially available flake/pellet food, you can offer them frozen foods or live prey.

This includes brine shrimp, blood worms, and daphnia. Live prey encourages your oscar to hunt for their food, just like they would in the wild. Seafood like clams, scallops, and squid make great additions to their diet and can be fed regularly.


You can also give them insects like locusts, crickets, and meal worms as Oscars eat a lot of insects in the wild.

In addition to meat-based foods, Oscars need some vegetables in their diet. Good options include spinach, peas, zucchini, and cucumber.

Mix up your oscar’s diet regularly and feed them a wide range of cichlid food to ensure they get all the nutrition they need.

What Is the Best Food for Them?

As Oscars eat a range of foods in the wild, you should replicate this in a home aquarium. Feed them a variety of food such as fish flakes/pellets, seafood, vegetables, and insects.

How Should I Feed Them?

Fish Flakes
Fish Flakes

You can simply add your oscar’s food to their tank when it is time for them to eat. No special tools or equipment are needed for feeding Oscars.

However, make sure you chop up any seafood or vegetables into bite-sized pieces before you offer them to your fish.

Additionally, blanch or boil any vegetables to make them easier for your oscar to eat.

How Many Times a Day Should I Feed Them?

You should feed your oscar fish two times a day: once in the morning and once in the evening. Only feed them as much as they can consume in around two minutes.

After this time, remove any leftover food to prevent it from polluting your water.


The best substrate to use in an oscar tank is sand or any other type of soft substrate. Crushed coral also works well.

Gravel can be used, but cichlids enjoy digging and sifting through fine substrates such as sand, so gravel might not work as well for this purpose.

Additionally, Oscars originate from the wild environment of South America (primarily in the Amazon River basin) in waters with muddy, soft bottoms. Using sand or other fine substrates in your oscar tank helps replicate their natural environment in the wild.


As Oscars can grow very large and have high bioloads, a high-quality filter is a necessity. I would recommend a canister filter for this cichlid species as they are much more powerful than other filter types.

Oscars do well in moderate to high water movement, just like their natural habitat in the wild. It is a good idea to use a filter with an adjustable water flow rate as this allows you to adjust the water movement in your tank.

Additionally, make sure your filter has a suitable water flow rate for the size of your tank. Ideally, your filter should be able to clean at least four times the capacity of your aquarium.

For example, if you have a 75-gallon tank, then you will need a filter with a water flow rate of at least 300 gallons per hour (GPH).


As Oscars are freshwater fish and originate from warm waters, they require heated water in their aquarium. To ensure their tank stays at a consistently warm temperature, you will need an aquarium heater.

There are many different types of fish tank heaters to choose from, including submersible heaters, hanging/immersible heaters, and in-line heaters.


Aquarium Led Light
Aquarium Led Light

Another piece of equipment you will require for a cichlid tank is an aquarium light. Any lamp will do the trick, so you do not need an overly strong lighting system unless you want to keep live plants.

The majority of aquarists keep their fish tank lights on for 8 to 12 hours a day to replicate a natural day and night cycle for their fish.

Keeping them on for longer periods than this can stress out your oscar and contribute to the growth of algae.

Plants and Decorations

Caves and crevices are a must for oscar tanks as it provides them with an area to retreat to within their territory. You can also add some bogwood and rocks to create a more natural environment.

As Oscars love to dig, they can easily uproot decor and plants. With this in mind, I would advise choosing hardy or floating live plants. Hornwort, anubias, java fern, and java moss are particularly good options.

Additionally, when stacking up rocks to form caves for this fish, you should pile them in a way, so they will not collapse. Using aquarium-safe glue can help make your caves more sturdy and secure.


If you are using any other decorations or artificial plants, affix them firmly to the tank as Oscars are quite destructive. This extends to equipment like heaters and internal filters, too.

What Size Tank Do They Need?

Oscars can grow to around 10 inches in size, so they require a fairly large aquarium to live in. For a single oscar, the bare minimum is a 55-gallon aquarium.

However, it is best to go for at least a 75-gallon tank.

Bigger is always better for this cichlid species, so try to get the largest aquarium you can afford. If you have a juvenile oscar, then make sure their tank is suitable for their adult size. Housing a young oscar in a small aquarium can stunt its growth.

Housing Recommendations

Like all aquarium fish, Oscars require specific water parameters in their tank. Let us take a look at the water requirements for these large cichlids so you can ensure your aquarium fits their needs.

Water Changes

Aquarium Water Change
Aquarium Water Change

One of the most important tasks you will need to do when keeping Oscars is water changes. Not only do these cichlids grow to a large size, but they also create a lot of mess and waste.

Leftover food, fish waste, and decaying plants can quickly pollute your tank water without proper maintenance.

This can cause a build-up of ammonia, nitrite, and nitrate, which can severely impact the health of your red Oscars.


Although a powerful filtration system can offload some of the work for you, it will not do everything. Regular water changes are mandatory for keeping any fish, but especially Oscars.

To change the water in your oscar tank, all you need to do is remove around 20% to 30% of old water and replace it with fresh (dechlorinated) water.

Most aquarists commit to weekly water changes, though your aquarium’s size and stocking choices will influence this frequency.


If you have a large and understocked aquarium, then you won’t need to do water changes as often as a small and overstocked tank.


Oscar cichlids are a freshwater species, which means they need tropical water to survive. You will need to make sure your oscar tank is fitted with an aquarium heater to ensure your fish has a relatively warm habitat.

You should keep your red oscar tank at around 77 °F, but make sure the temperature is always within the range of 74 °F and 81 °F. Extreme fluctuations in temperature can cause stress, as well as other issues.

Water pH Level

Wild Oscars come from South America in warm waters with a neutral pH, so they cannot tolerate extremes in alkalinity or acidity.

These large cichlids do best in aquarium water with a pH between 6 and 8, and carbonate hardness (KH) between 5 and 20. 


Make sure your pH is stable between this range at all times. Maintaining a stable pH is crucial as it can affect the toxicity of ammonia in your aquarium water. This can increase the chances of ammonia poisoning, which can be fatal.


No matter what species of fish you own, a good amount of work and time is necessary for keeping them happy and healthy.

After you have set up your oscar tank, made sure it has undergone the cycling process, and added your fish, there are various maintenance tasks you will need to do regularly.

Your oscar will need access to food a couple of times a day, ideally a wide range of foods to keep them healthy. They will also need their aquarium cleaned frequently to ensure the quality of their water doesn’t drop.

Daily Check

Additionally, it is recommended to frequently examine your fish for signs of illness or disease, as well as check your aquarium equipment for signs of damage. Lastly, you should test your aquarium water weekly to monitor your water parameters.

As you can see, Oscars are not a low-maintenance pet. They require quite a bit of work and care to ensure they live happy and long lives.

Are Oscars Aggressive?

Oscars are known for being aggressive and territorial, which is why you need to do some careful planning when choosing their tank mates.

Taking the time to consider who will be their tankmates can be the difference between life and death for some fish.

Will Oscars Kill Other Fish?

Oscars will bully, chase, and even kill other fish, especially if their tank is too small. They have also been known to kill other Oscars, though this doesn’t happen too often as long as the aquarium is big enough.

These cichlids are best kept with fishes that are a similar size to them, with temperaments that are neither too aggressive nor passive.

Why Do Oscar Fish Jump Out of the Tank?

In the wild, Oscars linger near the waterline to catch insects that might be present…

Oscars can jump out of their fish tank for many reasons, including poor water quality, lack of hiding spots, and lack of oxygen. If your oscar is attempting to jump out of their aquarium, then it could be due to any of these factors.

Catching Food

However, one of the most straightforward reasons Oscars jump is because they accidentally mistake something for food.

In the wild, Oscars linger near the waterline to catch prey such as insects that might be present.

In an aquarium, Oscars can mistake things such as water droplets falling off the rim for an insect, resulting in them jumping to attempt to catch them.

That is why you must have a tight-fitting lid or hood on your aquarium.


Additionally, Oscars are powerful fish and can knock off lids if they jump, so make sure your lid or hood has a latch for extra security.


Due to their large size and aggressive personality, housing these cichlid fish in a community aquarium can be problematic.

However, that is not to say it can’t be done as long as you do your research regarding appropriate tankmates.

What Kind of Fish Can You Put with Oscars?

Oscars can be kept in community tanks, but their tankmates need to be selected carefully. Small species of fish, shrimp, slow-moving fish, and small farlowella twig catfish are off-limits for this cichlid.

You should opt for large species of fish that can tolerate your oscar’s aggression, like the majestic Tiger Sorubim. Other good tankmate options include arowanas, large plecos (like the sailfin pleco), firemouth cichlids, silver dollars, green terrors, convict cichlids, bichirs, and jaguar cichlids.

Unsuitable Tankmates

Although there are various species of fish that can be housed with Oscars, some should be avoided at all costs.

Slow-moving, small, and overly passive fish, as well as shrimp and small catfish, should not be mixed with Oscars. The latter is especially true as plecos have sharp spines on their fins that can kill your oscar.

Pleco and Oscars

Pleco On Aquarium Decoration
Pleco On Aquarium Decoration

If your fish attempts to eat the pleco, then these spines can get lodged in their throats. Not only is this fatal to your oscar, but also your pleco.

African cichlids are also off-limits in a fish tank that houses Oscars, as both species have completely different temperaments and water parameters.

If you want to keep other cichlid species with your red oscar, select species from South America.

High Maintenance Fish

Fish that require a pristine and immaculate aquarium are also inappropriate for your cichlid tank. As I mentioned earlier, Oscars are messy fish that produce a lot of water, which can contribute to high nitrates in the aquarium.

Lastly, you should avoid species that are sensitive to aggression such as discus fish. Species that need a peaceful habitat will become stressed if they are kept with an oscar.

How Many Oscars Should You Keep Together?

Oscars do best when housed in pairs or small groups. If you have space, I would advise keeping at least 2. It is not recommended to house three as two of your Oscars could bond and bully the other fish.

Bear in mind that you will need an extremely large tank if you want to keep more than one oscar fish.


A single fish requires at least a 55-gallon to 75-gallon aquarium, but you will need to provide a minimum of 30 gallons per additional fish.

So, if you want a pair of Oscars, you will need at least an 85-gallon to 105-gallon aquarium.

Can I Keep Just One?

Oscars can live alone quite happily, so it is not a huge issue if you only have room for one fish.

Health Concerns

Despite being a relatively hardy and robust species of fish, Oscars are still prone to a few diseases and illnesses in the aquarium, including Hole in the Head Disease, Ich, Popeye Disease, and Fin or Tail Rot.

Signs of a Healthy Fish

Healthy Oscars should have vivid coloration, bright eyes, and a good appetite. They should be active and alert without displaying antisocial behavior like lying at the tank’s bottom.

Red Flags

If your oscar fish isn’t quite themselves, then there are many different signs that you will need to look out for.

This will help you figure out the cause behind your fish’s abnormal behavior and determine the best course of action.

  • Cloudy eyes
  • Lesions, cuts, or wounds on the body
  • Missing scales
  • Inflamed gills
  • Lethargy
  • Abnormal swimming pattern
  • Bloat
  • Respiratory distress
  • Clamped fins
  • Torn or fraying fins
  • Loss of appetite
  • Pale coloration
  • Stringy white feces
  • Antisocial behavior
  • Swimming vertically, upside down, or on the side

Why Is My Fish Turning Grey?

Oscar fish are known for changing to a grey color occasionally, particularly black Oscars. There are a few reasons for this occurrence, including stress, illness, or fear.

Additionally, this species can turn grey to blend in better with their habitat.

If your fish tank substrate is a light color, then your Oscars might change to a lighter color to help them fit in with their surroundings.

Common Illnesses and Diseases

Here is a little bit more information on a few of the most common ailments that can affect this species cichlids, including causes, symptoms, and treatments.

Hole in the Head Disease /Hexamita

Hole in the Head Disease (also known as Hexamita or Lateral Line Erosion) is quite a common disease that can affect fish, especially Oscars, discus, and other cichlid species.

See what hole in the head disease looks like below…


It is not quite clear what specifically causes this disease, but it has been linked to poor water quality and nutritional deficiencies.

Infected fish are often living in unclean environments or subjected to improper nutrition.

Deficiencies in Vitamin D, Vitamin C, calcium, and phosphorus are common among sufferers of Hole in the Head Disease.


This disease’s primary symptom is pit-like holes that form on the fish’s head, though these holes can also appear on other parts of the body.

Other symptoms include poor appetite, dull coloration, and stringy white feces. If left to progress, Hole in the Head Disease will spread from your fish’s body to the lateral line.


The best care methods for this disease are frequent water changes and a well-balanced diet. Make sure your fish is given a variety of foods, including vegetables, insects, flake/pellets, seafood, and frozen or live prey.

Regular water changes are also required for treating Hole in the Head Disease. Improving the quality of your aquarium water will give your Oscars a healthy and clean environment to recover in.


Clown Loach With Ich
Clown Loach With Ich

Ich is another common disease that can affect freshwater species of fish. It is caused by the Ichthyophthirius multifiliis parasite.

This disease is easy to spot as small white spots will form on your fish’s body. Some other signs of Ich are poor appetite, clamped fins, rapid breathing, rubbing against plants or tank decor, and lethargy.


One of the most critical aspects of Ich you need to be aware of is how contagious it is. This disease spreads very easily, so it is best to treat your entire fish tank even if symptoms are only present in one fish.

Popular treatments for ich are salt baths, increasing the temperature of your fish tank, and using malachite green medication.

Popeye Disease

Popeye disease in fish is caused by extremely poor water conditions. Its primary symptoms are a bulging or swollen eye (both eyes can also be affected) and cloudy eyes.

Treating this disease can be difficult, but you will need to improve the quality of your water and use an antibiotic medication for aquarium fish.

You can also add aquarium salt at a dose of 1 tablespoon per 5 gallons of water.

Loss of Eye

Unfortunately, some Oscars lose their affected eye if the damage is too serious. This can occur even if you manage to successfully treat your fish. On the plus side, a lot of fish can live perfectly happily with one eye.

However, if your fish loses both its eyes, then you will need to make sure they can feed and swim properly.

Breeding Process

Oscars are hard to breed in home aquariums, but that is not to say it can’t be done. If you are set on breeding Oscars, then it is a good idea to purchase an established breeding pair.

Alternatively, you could buy a group of juvenile Oscars and let them grow together and form mating pairs.

But bear in mind that there’s no guarantee your group of fish will pair off together, or even contain males and females. Oscar juveniles also take around one to two years to mature.

Tank Setup For Breeding

Once you have got a mating pair, you will need to make a few adjustments to your tank. These cichlids reproduce in the rainy season in their natural, wild habitat. To replicate this in your aquarium, you should lower the temperature a couple of degrees. 

Water changes every two days and siphoning the gravel, as well as a well-balanced diet will also help induce spawning behavior.

Spawning Process

When your fish are ready to spawn, they will flare their gills and wag or vibrate their fins to indicate to their mate that they want to breed.

Both Oscars will clean a rock surface to provide the female with a spawning place.

Small females may only produce 300 to 500 eggs during spawning, but larger females can produce up to 2,500 to 3,500 eggs.


The parents will protect the eggs until they hatch (usually after two to three days). The female will fan the eggs to stop them from being smothered by the substrate, while the male will ward off other species of fish.

Unfortunately, it is not uncommon for Oscars to eat their eggs. This can occur if the eggs are not fertilized or if the pair feel unsafe or distressed.

See how the eggs look and how they hatch in the video below…

Tiger Oscar Fish Breeding at HOME I Oscar Fish Eggs Hatching I

Oscar Fry Care

Before the eggs hatch, you will need to decide whether you want to separate the fry from their parents or move them to a separate tank. If you have space, it is best to move the fry to another aquarium to prevent them from being eaten.

Once the eggs have hatched, the fry will consume the remains of their egg sac for four days and will not need to be fed.

After this time, you can begin to feed them. Use insofuria initially and then move to baby brine shrimp within a week.


Feed the baby Oscars three times a day. In the wild, oscar fry will stay with their parents until they grow to around 1 inch in size. However, it is best not to keep oscar fry with their parents to prevent them from being eaten.

As your oscar fry grow, you will need to move them to a larger tank to ensure their growth is not stunted.

What Do Oscar Fish Eggs Look Like?

Fish eggs for this species are an opaque white color.

However, if the eggs are fertilized, they will be a tan or light brown shade.


Owning Oscars is a rewarding experience, but one that takes a large amount of time and work. This species is best suited to experienced aquarists as their care needs can be a little overwhelming and complicated for those new to keeping fish.

Oscars come from waters in South America, so they need warm water to survive, as well as a neutral pH. As they can grow up to 10 or 12 inches in size, this species needs a large tank that is at least 55 gallons in volume.

Diet and Temperament

Due to their omnivorous natural feeding habits, you will need to feed this fish a variety of foods like insects, seafood, vegetables, live/frozen prey, and pellets or flakes. Feed them two times a day: once in the morning and once in the evening.

As Oscars are aggressive, they should be kept with species that are a similar size and temperament.

Arowanas, silver dollars, jack dempsey cichlids, convict cichlids, and large plecos are some good choices.

Tank Size

You can keep one, two, or small groups of these fish.

Just make sure their aquarium is big enough for them to grow in and contains lots of natural cover and hiding places.

As long as you have the time and patience to care for Oscars, I think they are an excellent fish to own.

Not only are they striking in terms of appearance, but they also have interactive and interesting personalities that a lot of other freshwater fish lack.

Share Your Thoughts!

Do you own Oscars? Thinking of starting an aquarium or need some tips? Get in touch with me via social media and share your pictures, tanks, and ideas with me!

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