Looking After Your Oscar Fish

Scientific Name: Astronotus ocellatus (Cuvier, 1829)

Previously Known as: Acara ocellatus, Acara crassipnnis, Cychia rubroocellata, Hygrogonus ocellatus, Lobotes ocellatus


Genus: Astronotus

Common Names: Velvet Cichlid, Oscar, Red Oscar, Tiger Oscar, Black Oscar, Marbled Cichlid & Peacock Cichlid;

Note: Peacock Cichlid is a misnaming being confused with the “Peacock Bass” ( Cichlasoma ocellaris)-bass in name only- due to the ringed caudal peduncle “spot” marking. Similar to the eye spot marking of a peacocks tail feathers. Interestingly enough captive bred Oscars generally exhibit a single eye marking whereas wild specimens may exhibit several.


Eastern Venezuela, the Guianas, and the Amazon Basin to Paraguay. Accidentally introduced into canales and water channels of Florida by local fish farmers and hobbyists where they are now feral and compete with native species. However I understand they make great sport for some anglers.

Oscars are ambush predators and are fond of mud-covered canales, rivers and ponds. Most of the Oscars seen in the hobby today are captive bred though some wild caught specimens are available from time to time


In captivity it is not uncommon for Oscars to attain a length of 12 inches with wild specimens reported at 15 inches plus. They reach breeding size at about 4 -7 i-7 inches and with good captive conditions this may be possible within 18 months.

The lifespan of an Oscar varies depending on husbandry and diet, though eight to ten years is not uncommon with attention to good aquarium practices.

Experienced Oscar breeders can ascertain correct gender based on circumstantial posturing, size and tube shape.

Venting is an absolute way of determining the sex of an Oscar but is not recommended by the author for it is to stressing to the fish and can be harmful to the person handling it if handled incorrectly.

During spawning, the male’s tube is “pointed” whereas the females are “rounder & flatter”. Though physical differences are subtle, males are generally more colorful and larger with a more rounded cranial profile while females have a more compressed body shape.

Social Behavior/Personality:

Oscars are victims of a brutish mug. Opportunistic piscivores, Oscars will make a meal of anything resembling a would be food item including tank mates that are small enough for the fish to get its mouth over and what a large mouth they have.

For its size, Oscars are remarkably non-aggressive (compared to many other large cichlids), inquisitive and by some are considered to be the most intelligent of aquarium fishes. They should never be kept with African cichlids as they may harass and stress your fish to death.

I have been told that they show signs of affection, creating attachments to fish other than Oscars. With a seemingly show of sensitivity, they have been said to recognize their owners though some disputed this as a conditioned feeding response in connection with familiar and regular feeding patterns by its keeper.

Some might suggest that these fish can become "hand-tame". Never underestimate the temperament of your Oscar; they seem to vary from one individual to another. Most do respond quite favorably to lots of attention.

Temperature/Water Chemistry/Filtration:

Fortunately for the Oscar and those of who enjoy keeping them, they can withstand a wide range of water conditions. A temperature of 72-80 degrees F is the norm. Sometimes a temperature of 82-85 degrees F is helpful in inducing spawning behavior.

Extremes should be avoided; they have a hard time surviving the cold, while high temperature extremes without proper aeration will cause oxygen depravation that may lead to death.

A pH of 6.0-8.0 and a hardness of 5-12 degrees are acceptable.

Water changes are the only way of insuring good water conditions and good health for your Oscar. Ammonia, Nitrites and Nitrates can be controlled with weekly-biweekly water changes of 30-40% along with GOOD filtration.

There is no such thing as "over" filtering an Oscar tank. With the many types of available, it shouldn't be too difficult to find one that will meet your needs. Avoid using under gravel filters with sub-adults and adults as they will dig and sift through the substrate and cause dead spots or even a total non-function of this type of filter.

Almost all filtering systems may be enhanced by the use of chemical removing items such as HBH’s Ammonia and Phosphate removing pads. To also help clear up yellow water and reduce some traces of ammonia HBH’s Carbon impregnated pads should be used. Always vacuum gravel.

Aquarium Size/Décor:

The size of your aquarium should be matched to the current and the soon to be size of your fish. I would suggest getting into the largest tank you can afford. Juveniles can be kept in 20-50 gallons as well as single adults; pairs should be kept in 60+ gallons.

The more room you provide your fish the more apt they are to spawn due to a sense of security and available hiding places. I have heard of people keeping them in less but the author does not recommend it. For optimum health of your fish tank size is a big one. It also aids in good water quality.

Forget about live plants! If you must insist on having live plants in your tanks they should be potted with large rocks covering the potting substrate and roots to help prevent up rooting. This will not stop the devastation experienced by the exposed foliage. With Oscar tanks, rocks, gravel and artificial plants are the only way to go.

Be sure not to include rocks with sharp edges as they may cause serious injury and or scaring. In any case however you decide to decorate your tank, your Oscars will surly redecorate it for you.

Diet: Lastly, maybe an algae eater. They'll just help keep things a little bit cleaner.

Oscars are chowhounds and quite accomplished beggars too, but sometimes they can be finicky, especially if you feed your fish one diet exclusively. Most of the Oscars I have kept will eat almost anything offered them. A good varied diet consisting of HBH’s Oscar Bites and Cichlid 4 Flake Frenzy for Juveniles, Oscar Grow and Cichlid 4 Flake Frenzy for sub-adults and Oscar Show along with Cichlid 4 Flake Frenzy, Super Cichlid sinkers and Super Cichlid Floaters for adults will insure the best of health for your fish.

There is just one side effect of feeding prepared foods; they don’t transmit disease and or parasites.

In the wild Oscars do eat a wide variety of live foods and will stalk, ambush and even scavenge for a meal.

It is important to note that over feeding may cause some of the same health problems experienced in humans and will contribute to poor water quality such as high phosphate and ammonia levels.

Physical Description/Breeding:

Captive Oscars seem to come in almost any color and pattern you can imagine including olive to nearly black, orange/red to rust flaming all around them, not to mention albino forms. They are round, thick, robust fish with overlapping caudal and anal fins sporting a ringed "eye" spot located at the base of the caudal peduncle and equipped with a large fleshy-lipped mouth.

They also have a broken lateral line as is typical of all cichlids.

Spawning Oscars isn’t as hard as it might seem, that is once you have a pair. The easiest way to obtain pairs is to purchase 6-8 juveniles and wait for pairs to form. Once you have a compatible pair, the female will begin by cleaning and then laying a plaque of eggs, typically 1000-2000, on a predetermined site. Acceptable spawning sites consist of flat rocks, side of the tank, slate and up side down flowerpots.

The male will follow by fertilizing the eggs and upon completion of this both parents will help in brood care and protection. It is at this time a hiding place for the female is helpful as the males can become quite abrasive at times.

Parents fan the eggs to help oxygenate and keep them free of bacteria and detritus, the eggs are also mouthed to aid in keeping them clean and removing the infertile ones as fungus may attack the developing eggs. Oscars will sometimes keep the fry in depressions or "pits" cleared in the substrate by the parents, furthermore the fry may even be covered. Eggs hatch after about 36-48 hours and after the yolk sacks are absorbed they can begin feeding on crushed HBH Fry Bites, crushed Cichlid 4 Flake Frenzy and freshly hatched brine shrimp due to their large hatching size.


Oscars require planning; don’t let their cuddly appearance as juveniles fool you. Large fish carry with them a large responsibility and as with any pet you owe it to yourself and them to learn as much as possible about the creatures you care for. Education is the key to a successful fish keeping experience.