Astronotus ocellatus – Oscar

You can find the Astronotus ocellatus or Oscar by its common name, in a vast area in South America. They inhabit the river basins of the Amazon and Orinoco rivers.

Astronotus ocellatus – Oscar

Shops will usually sell the Oscar when they are very young, up to 7 centimeters. Pay attention! They will grow up to 35 centimeters in total length!

The difference between males and females is hard to tell. You can identify the adult female by her oviposter when she is ready to spawn. Sometimes male have dark stripes at the base of their dorsal fin. When they are for sale in the shops they are rather small and brightly colored but the are fast growing. When they mature they lose some of the bright coloring, the black dot on their caudal fin remains.


Rio Paraguay, Rio Negro, Rio Paraná, Argentinië, Peru, Brazilië, Frans Guyana, Amazon.

You can find Astronauts ocellatus or Oscar by its common name, in a vast area in South America. They inhabit the river basins of the Amazon and Orinoco rivers in French Guyana, Paraguay, Peru, Colombia, Uruguay and Venezuela. The Oscar can be found in clear water, black water, murky water, still or slowly flowing water, ponds, streams, rivers but they also inhabit the flood plains.

Usually they live over a sandy substrate littered with driftwood and rocks, sometimes combined with plants. Since the study by Kullander in 1986 we believe the variety from Paraguay to belong to the Astronotus crassipinnis species. Besides the “eye” on the caudal penducale they also show eyespots on their dorsal fin.


You will need an aquarium of at least 2 meters length if you want to keep Astronotus ocellatus. You can decorate the aquarium with a thick layer of rounded fine gravel, driftwood, rocks and some strong plants. They like to dig into the substrate and play with the roots and plant. To protect the plants you can put them in pots and put some heavy rocks on top of these pots.

Because they like to dig in the gravel and consume large amounts of food, you will need an excellent filtration system and very regular water changes. Make sure you have a lid on the aquarium as they are excellent jumpers.


Temperature: 23-26 degrees celsius.
PH: 6-6,5
GH: 8-12

In nature fish experience fluctuating temperatures. Keeping the fish for longer periods on their minimum or maximum temperature may shorten their life span.


Astronotus ocellatus has a slightly upward beak which is wide and big. It can eat large chunks of food at a time. In the wild they will eat fish, crayfish, insects (they will sometimes even jump out of the water to get one), musquitos and insect larvae. In the aquarium they will need a varied diet that may consist of fish, squid, mussels, krill, white- black or red mosquito larvae, cichlidsticks, etc. They seem always to be hungry so be careful not to overfeed them.

After a heavy meal the Oscar may take its time to digest its food. They may lay down on the bottom so don’t panic when this happens.

Warning: Don’t keep them together with Corydoras, they will try to eat them en choke on the Corydoras as they will use their spiny rays for defense.

Astronotus occelatus is sensitive to hole in the head disease. To prevent them getting this disease you can add Vitamine C to their food.


Oscars are large, peaceful territorium creating fish, they are peaceful to other species but also to other Oscars. You can keep them as a pair or as a group as long as you keep them with other large cichlids or catfish. Smaller fish will be very expensive food to them.

Breeding Astronotus ocellatus – Oscar

Sexing the Astronotus ocellatus is only possible when they are spawning. If you want to breed the Oscar it is best to start with 4 or more fry and raise them together. Eventually a couple wil emerge from the group. Preferable use different bloodlines to prevent inbreeding.

Eggs are deposited on a flat rock or boulder. The 500 to 1000 eggs are yellowish/white and somewhat sticky. They will hatch in a couple of days. The parents will move the fry to previously dug pits. The first couple of days you can feed the fry with cyclops and newly hatched brine shrimp. As they grow you can start giving them larger foods, as long as it fits their mouths it is ok. The fry will grow rapidly.

Fishfarms have created several breeding forms of the Oscar like the orange/red albino Oscar.



Coby – J. de Lange

Copyright images

J. de Lange
Ben Lee –

Last Updated on 6 October 2021 by John

Additional information





Social Behaviour

Breeding behaviour





, ,



Length minimum in cm

Length maximum in cm

Temperature minimum

Temperature maximum

pH minimum

pH maximum

GH minimum

GH maximum


There are no reviews yet.

Be the first to review “Astronotus ocellatus – Oscar”

Your email address will not be published. Required fields are marked *