Oscar

Tiger Oscar, Velvet Cichlid, Marble Cichlid

Family: Cichlidae Oscar Cichlid, Astronotus ocellatus, Tiger Oscar, Velvet Cichlid, Marble CichlidAstronotus ocellatusPhoto © Animal-World: Courtesy David Brough
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is it safe to feed feeder fish Oscars? some people say feeder fish have diseases.  Anonymous

A classic in every sense of the term, the Oscar Cichlid has long been heralded as one of the most spectactular and iconic of the aquarium fish!

The Oscar Astronotus ocellatus is a large, boldly colored South American cichlid characterized by its unique personality and striking intelligence. These handsome fish quickly grow to a maximum size of a little under a foot (12" or 33 cm)  and are experts at commanding the attention of anyone observing their tank. 

Oscars are certainly some of the most personality driven fish in the hobby, and can actually have so much personality that their territory may extend beyond the tank. They will investigate any goings on in the room and can bond with their owners on a level that the smaller cichlids don't. They can be taught to roll over for food and can even learn to enjoy being petted. Sometimes they act prideful or spoiled and can be sensitive or moody. This fish can also be demanding, behaving just like part of the family!

The adults in the wild are normally a dark color with orange around the gills, on the sides towards the back, and with an orange-ringed black spot at the base of the caudal fin. The scientific description of this fish is truly fitting. The genus term Astronotus means "ray-backed, star-marked" and the species term ocellatus means "spotted or eye spot". Several common names used for this fish are also quite indicative of its appearance including Tiger Oscar and Marble Cichlid. In earlier times they were actually referred to as the 'Velvet Cichlid'.

Though wild caught Oscars are still popular and widely availabe, a number of striking and dramatic color forms have been developed and are similarly popular and available. While all of these color forms present unique and beautiful aesthetics, perphas the most attractive is the mostly solid red colored Red Oscar. Similarly, the Speckled Red Oscar, with a speckled solid red body and black fins, is another contender for the most dazzling color form. 

Other popular tank bred varieties include the Tiger Oscar which is very similar to the wild form but with more red coloring, and the Red Tiger Oscar with marbled patches of red pigmentation. The Albino Tiger Oscar, Albino Red Oscar, and all the various lutino and long finned varieties are also some more recently developed forms. In addition, some Oscars have even been artificially colored or 'painted' to increase their appeal. In short, there is no shortage of interesting and dramatic coloring and patterning of these fish, so no matter what you like you will probably like the Oscar!

Luckily for the fish keeping world and its popularion of more or less experienced aquarists, Oscars are very easy to keep and make a great beginner fish. The only aspects of their care which might be difficult for a beginner are the facts that they grow very large very quickly and are not meant to be kept with other fish. As a large, predatory cichlid, they will need to be kept in an aquarium of at least 100 gallons or larger and will eat almost any other fish in their aqarium. It is thus recommended to only keep them either individually, as a breeding pair, or as a community member in a very large aquarium. 

Oscars are curious fish that love to play. Rocks make a good decor but must be securely placed on the glass bottom as this fish likes to rearrange its home. Live ground plants can be a challenge because they can be uprooted, floating plants or plastic plants often work better. They also like to explore new things and will enjoy an occasional 'toy' like a plastic ornament. They can live 10 years or more with proper care.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

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Geographic Distribution
Astronotus ocellatus
Data provided by FishBase.org
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Perciformes
  • Family: Cichlidae
  • Genus: Astronotus
  • Species: ocellatus
Big Oscar Fish

Oscar - Quick Aquarium Care
  • Size of fish - inches: 14.0 inches (35.56 cm)
  • Minimum Tank Size: 100 gal (379 L)
  • Temperament: Large Aggressive - Predatory
  • Aquarium Hardiness: Moderately hardy
  • Temperature: 72.0 to 77.0° F (22.2 to 25.0° C)
  • Aquarist Experience Level: Beginner
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Habitat: Distribution / Background

The Oscar Astronotus ocellatus was described by Agassiz in 1831. They are found in South America; the Amazon River Basin, the Parana, the Rio Paraguay, and the Rio Negro. This species is not listed on the IUCN Red List. Other common names they are known by are Tiger Oscar, Velvet Cichlid, and Marble Cichlid.

The many captive bred color variety names are based on developed coloration and patterning, with some of the best known being the Red Tiger Oscar, Red Oscar, Speckled Red Oscar, Albino Tiger Oscar, and Albino Red Oscar. Other more recent varieties are lutinos and long-finned. There are also some that have even been artificially colored or 'painted' to increase their appeal.

Oscars have been introduced into natural waterways in China, Australia, and Florida as a by-product of the aquarium trade. Expansion into many non-native areas is somewhat restricted as they are intolerant of cooler water temperatures. They are a highly valued as a food fish in South America.

They inhabit slow moving waters of rivers, canals and ponds with muddy or sandy bottoms, feeding on small fish, crayfish, worms and insect larvae.

  • Scientific Name: Astronotus ocellatus
  • Social Grouping: Pairs - Though they begin life tolerating group living, they tend to become more solitary as they age and should be kept individually or in pairs.
  • IUCN Red List: NE - Not Evaluated or not listed

Description

The Oscar Cichlid has an oval shaped body and large thick lips. They are known to reach up to inches 12" (33 cm) in length in the wild, though they are usually a bit smaller in the aquarium. They have a life span of 10 years or more with proper care.

Wild caught Oscars are typically darkly colored with some orange around the gill area and on the sides towards the back, and with an orange-ringed black spot at the base of the caudal fin. Both captive bred and wild caught specimen are known to rapidly change their coloration when becoming territorial, combative, or when experiencing large amounts of stress.

Juveniles display white and orange wavy bands or stripes and have spots on their heads. There are many varied color forms of captive bred Oscars. They can be marbled, mottled, blotched, red and black, all red, and all black.

  • Size of fish - inches: 14.0 inches (35.56 cm)
  • Lifespan: 10 years

Fish Keeping Difficulty

Though Oscars can make for an entertaining and interesting beginner fish, it's important to not be fooled by their initial small size and seemingly social behavior. Most Oscars for sale in pet stores will be about 1" (~3 cm) long and probably kept in a small tank with a variety of other oscars and cichlids. However, don't let these little fish fool you into taking one home and trying to raise it in a ten gallon or community tank. Oscars grow quickly and will require a tank of least 100 gallons and will incur fairly expensive feeding costs once they are full grown. In addition, they are predatory and should not be kept with other fish unless as a mated pair or in a very large tank. 

Don't be discouraged however! If you find this is the fish for you, they are actually quite easy to take care of from a feeding/tank maintenance standpoint and are perfect for the diligent, prepared, and properly informed beginner!

  • Aquarium Hardiness: Moderately hardy
  • Aquarist Experience Level: Beginner

Foods and Feeding

The carnivorous carnivorous Oscar is a hearty and uncomplaining eater. They prefer to be fed a variety of live, meaty foods, but will readily eat pelleted, dead, or frozen food if offered. They grow quite large so they should be fed a high quality pelleted food and large chunk foods such as cut up prawn and earthworms. As they grow larger, they will particularily enjoy live foodstuffs such as goldfish, guppies, and worms. 

Meats from warm blooded mammals (e.g. poultry, beef hearts, pork, etc) were once considered a staple in the diet of all large ciclids. However, more recently it has been discovered that due to the high amounts and types of fats and proteins contained in these foods, (which do not occur naturally in a wild cichlid's diet) these foods should not be fed to cichlids. The fats and proteins contained in these foods can cause damage to a cichlid's organs and lead to dangerous intestinal blockages. If you find your fish enjoys these types of foods, be certain to feed them only as an occasional treat, not as a main course. 

  • Diet Type: Omnivore
  • Flake Food: Yes - More common when young.
  • Tablet Pellet: Yes
  • Live foods (fishes, shrimps, worms): Some of Diet
  • Vegetable Food: Some of Diet
  • Meaty Food: Most of Diet
  • Feeding Frequency: Several feedings per day

Aquarium Care

Speckled Red Oscar, Astronotus ocellatusSpeckled Red Oscar Photo © Animal-World: Courtesy David Brough

Oscars are fairly easy to care for provided their water is kept clean. Aquariums are closed systems and regardless on size all need some maintenance. With home aquariums the nitrate and phosphates build up over time and the water hardness increases due to evaporation. Because these fish are very sensitive to pollitants and pH instabilty, so it is important that at least 20-40% of the tank water should be replaced weekly, especially if the tank is densely stocked. When doing the water changes always use a gravel cleaner to make sure all of the decomposing organic matter that has built up is removed. The majority of of problems that occur with tropical fish tanks usually come down to one cause, decomposing organic matter.

Keep in mind that Oscars are VERY messy eaters and the nature of their diet will likely have an impact on the timing and frequency of tank cleaning.  For instance, Oscars tend to spit out parts of live fish while generally eating the entirety of pellted foods. So if feeding live fish, it is likely you will have to clean their tank more thoroughly and more often. 

  • Water Changes: Weekly - May need more frequent depending on stock and feeding habits.

Aquarium Setup

A juvenile Oscar can be comfortably kept in an aquarium as small as 30 gallons, but once they are fully mature they will require at least 100 gallons or more. If you are planning to keep them as a breeding pair or with other large cichlids, you will want a significantly larger tank to maintain low levels of aggression. Oscars require a high level of oxygen but do not prefer living with a lot of water movement, so it is recommended to provide one or more airstones in their tank, more or less depending on the size of the tank. 

As with most large and active fish, make sure equipment such as heaters and inlets and outlets are either well hidden or protected by immovable objects. Heaters should either be kept externally or secured behind a large rock or some other type of heavy obstruction. Oscars tend to like to "play" with the decor in their tanks and due to their size and aggressive tendencies are actually known to cause significant damage to delicate pieces of equipment. One possible solution or way to at least lessen this problem is to provide your fish with toys, something to grab its attention, and let it play with that instead.  

They appreciate a bottom of fine sand and plenty of hiding places among rocks and wood. They are avid diggers and plants don't fare so well as they will be eaten or shredded. Make sure rocks are well bedded on the actual glass bottom of the tank to prevent toppling. Do not try to keep an over manicured looking decor as far as decor, Oscars will move and rearrange your hard work!  Floating plants make great cover for Oscars. Leave an open area in the center for swimming. Make sure to have a tight fitting secure lid to prevent the Oscars from jumping out of the tank and splashing when eating. 

  • Minimum Tank Size: 100 gal (379 L)
  • Substrate Type: Sand
  • Lighting Needs: Moderate - normal lighting
  • Temperature: 72.0 to 77.0° F (22.2 to 25.0° C)
  • Breeding Temperature: - 78.8 - 86° F (26 - 30° C)
  • Range ph: 6.5-7.2
  • Brackish: No
  • Water Movement: Weak - Provide at least one air stone to supplement the oxygenation of the water as though Oscars prefer slow moving water, they also require the high oxygen levels normally incurred by quicker moving water.
  • Water Region: All

Social Behaviors

Oscars are not a community fish. Even though they are not generally belligerent and aggressive towards other fish, they are predatory and will seek to eat most tankmates. That being said, it's not impossible to keep Oscars with other fish. They simply require other, large fish as tank mates and must be kept in a sufficiently large aquarium (at least 200 gallons or more). For instance, some aquarists have reported keeping Oscars, Black Pacus, Arowanas',  Jack Dempseys, and large Plecostomus in the same tank for long periods of time. 

Oscars like to dig up plants and love to play with toys and rearrange their tank's decorations. They are also one of the most amicable fish around in terms of bonding with their owners. They like to watch what is going on in the room and are known to beg for food, react to the voices of their owner, and even perform tricks like rolling over! 

  • Temperament: Large Aggressive - Predatory
  • Compatible with:
    • Same species - conspecifics: Yes - Will get territorial as they age.
    • Peaceful fish (): Threat
    • Semi-Aggressive (): Monitor - May be OK with similiar sized and in a very large tank.
    • Aggressive (): Monitor
    • Large Semi-Aggressive (): Monitor
    • Large Aggressive, Predatory (): Monitor
    • Slow Swimmers & Eaters (): Threat
    • Shrimps, Crabs, Snails: Threat - is aggressive
    • Plants: Monitor

Sex: Sexual differences

They are difficult to sex. The easiest method is to obtain six to eight juveniles and let them pair off on their own as they reach sexual maturity.

Breeding / Reproduction

Oscars have been extensively bred in captivity and are sexually mature at about 4 1/2 inches (11.4 cm). They are egg layers and open spawners. Give the pair a large amount of room in their own breeding tank, 100 gallons or more is preferable. Provide flat smooth stones as a spawning substrate.

The breeding water can be soft or hard, as long as it is clear and clean, with temperatures between 78.8 - 86° F (26 - 30° C). The female spawns 1000-2000 eggs on carefully cleaned rocks. They are excellent parents and the brood is protected and cared for by both. The fry are kept in a pit and sometimes covered. Free swimming fry can be fed Cyclops. See the description of how these fish breed in: Breeding Freshwater Fish: Cichlids for monogamist cichlids.

  • Ease of Breeding: Moderate

Fish Diseases

The only disease they are particularly vulnerable to is Head and Lateral Line Erosion (HLLE), a.k.a. "hole-in-the-head" disease. This looks like cavities or pits on the head and face. It is believed this may be a nutritional deficiency of one or more of: Vitamin C, Vitamin D, calcium, and/or phosphorus. It is thought to be caused by a poor diet or lack of variety, lack of partial water changes, or over filtration with chemical media such as activated carbon.

As with most fish, Oscars should be monitored diligently for disease or injury. Though very durable it's a good idea to keep an eye out for skin flukes and other parasitic infestations (protozoa, worms, etc.), fungal infections, and bacterial infections. It is recommended to read up on the common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.

Remember anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria or damaging chemicals. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance.

Availability

Oscars, under the various names mentioned above, tend to be readily available either as a wild caught fish or in tank bred color varieties. Juveniles are usually not very expensive, though adults cost a bit more.

References

Author: Clarice Brough CFS
Lastest Animal Stories on Oscar


Anonymous - 2014-11-07
is it safe to feed feeder fish Oscars? some people say feeder fish have diseases.

  • Clarice Brough - 2014-11-07
    Feeder fish are just like all other fish, they are subject to disease. It is best to set up a quarantine tank to keep feeders in and only feed them after a 2-3 weeks once you are certain they are not sick.
Reply
Anonymous - 2014-11-06
can tiger Oscars be fine with pangasis catfish? I have a 55 gallon tank with two Oscars and one pleco.

  • Clarice Brough - 2014-11-07
    I wouldn't suggest it, these fish all get big. Your tank is way to small, even for the Oscars, and pangasius are very skittish fish.
Reply
Wilson - 2014-03-12
Okay well I have a 100 gal fish tank with a 7-8 in tiger Oscar and a breeding pair of jaguar cichlids, a gar and a convict and a red tail catfish. The Oscar ran the tank until about a few days ago I started to see that the Oscar was acting different. He didn't swim much anymore which he was very active before. The male jaguar and he will flare out at each other, never fight but now the Oscar is just acting terrified. Should I get rid of the female jaguar to calm Jim down? Or what should I do? Also my baby Jack Dempsey which was active at all times stop being active? What's going on? :/

  • Jasmine Brough Hinesley - 2014-03-13
    Hmm, maybe your tankmates are just starting to become more aggressive and territorial. As they get older and/or ready to mate they sometimes will become more aggressive. It might be a good idea to remove the one jaguar cichlid and see how the other fish react. Maybe that will change the dynamics of the tank in a positive way. Are there plenty of hiding places as well? I would make sure there are lots of plants and other distractions where the fish can go.
  • Bryan - 2014-04-11
    Your tank is WAY overstocked. An Oscar, gar, and red tail catfish are going to get HUGE.
  • Rick McCloy - 2014-10-19
    I suspect that your problem comes down to your mannies now breeding, which greatly increases both their territoriality, and level of aggression. This will happen later with your J.D.s as well, if they form a pair. You will have to address it by keeping any breeding pairs in separate tanks of adequate size; your jaguars will need alot more space than will a pair of JDs. Although much smaller than I would like, I suggest that you keep the mannie pair in their current tank, and keep the oscar, and only one JD in a tank of about 135g. You can add one of the smaller plecs to this, or 2-3 striped raphael cats, which are basically indestructible, and remain at a manageable size.----rick
Reply
some fish lover! - 2009-11-28
I have two oscars, two red belly pacus, two jack dempseys, one black banded leporinus, one pufferfish, and one pleco in a ten gallon tank and they are doing fine! The oscars will eat anything that can fit in their mouth. Happy fish keeping!

  • Dsgsd - 2011-11-11
    I sincerely hope you have something along the lines of a 900 gallon tank for when EVERY SINGLE FISH IN THAT TANK OUTGROWS IT!
  • Trevor - 2014-08-09
    Please tell me that you're joking.
Reply