Astronotus ocellatus (Agassiz, 1831)
Suggested pronunciation: ass-trow-NOTE-uss oss-ell-ART-uss

 

PROFILE ________________ Common name Oscar, Velvet Cichlid ________________ Adult size in the aquarium.... they may reach up to35 centimetres in the wild.... may reach up to 45 centimetres ________________ Sexing Sexes are only distinguishable at spawning times when the female has a more obvious, rounded genital papilla. ________________ Diet Omnivore in the aquarium.... Oscars have a voracious, somewhat indiscriminate appetite. Floating or sinking Cichlid pellets, frozen bloodworm or cichlid dinner are suitable. There is a specific Oscar food available (HBH Oscar Show), which brings out the colour. Live crickets or mealworms can also be fed occasionally. in the wild.... The natural diet of Oscars consists largely of smaller fish, including Corydoras, crustaceans such as crayfish, gastropods, and aquatic insects or insect larvae. Although oscars are generally sluggish or inactive, they are capable of ambushing and capturing fleeing prey over short distances. ________________ Swimming level They mainly inhabit the middle and bottom regions of the tank ________________ Recommended for Beginners to experienced fish keepers; large cichlid community tank; sole inhabitant tank.

Rating Availability Hardiness Overall appeal

Species description

• Physical description....
  • Astronotus ocellatus is a large, stocky cichlid with an oval shaped body and moderate lateral compression.
  • They have a large head, large eyes, and a large mouth.
  • The mouth has thick lips.
  • The eye is generally black but, depending on the variety may be red.
  • The caudal fin is rounded, while the anal and dorsal fins are often pointed.
  • The dorsal fin has a number of hard rays at the front, with soft rounded rays behind.
  • The base of both the soft dorsal fin and the anal fin is scaled.
  • The pectoral fins are large and paddle-like.
  • The pelvic fins are quite long and have a thin extension of the first fin ray.
  • Te fins are the same colour as the body.
  • The wild Oscars have an olive-green to chocolate brown body colour with a mottled pattern of cream.
  • Most varieties are characterised by at least one eye-spot on either side of the base of the caudal peduncle. Some fish have more than one.
  • Juvenile fish are gray to black in colour with a pink marbled-ring pattern on the body.
• Taxonomy....
  • Kingdom: Animalia
    • Phylum: Chordata: Sub-phylum: Vertebrates - Group: Fish
      • Class: Osteichthyes (Bony Fish): Sub-class: Actinopterygii (Ray-finned Fish)
  • Order: Perciformes (Perch-like Fish)
  • Family: Cichlidae (Cichlids): subfamily: Astronotinae
    • Genus: Astronotus
      • Species: ocellatus
• Geographical variants....
  • There are no wild geographical variants.
  • A number of artificially selected aquarium colour varieties exist including Albino, Red Tiger, Tiger and Red Oscars.
  • A Long-finned variety is also available.
  • Images:
    • Long-fin Oscar (below left); Albino Red Oscar (below right)

• Similar species....
  • The Oscar is a very distinctive fish.
    

Habitat information

• Astronotus ocellatus is found in the Amazon River basin in Peru, Colombia, Brazil. Also known from French Guiana.
• They prefre to inhabit quiet shallow waters and occur in areas with mud or sand substrates where there are sunken branches and logs for cover.

Aquarium care
The following information relating to tank size, decoration and tank mates is indicative and intended to be used as a rough guide only. Other possible tank mates are listed under Compatibility and there are many plants and decorations that can be used - just ask us.

• Tank ideas....
  • A tank measuring 80 centimetres with a capacity of around 100 litres is sufficient for small Oscars under 12 centimetres in length.
  • Adult fish require a tank measuring at least 180 centimetres with a capacity of at least 360 litres.
  • Example - Oscarcommunity tank
    
    • Tank capacity: 460 litres
    • Tank type: HR-1800B
      • 180 centimetres (72 inches or 6 foot) tank
      • 1 x 40W; 2 x 30W; 2 x 20W fluorescent tubes
    • Fish ideas:
      • 2 x Astronotus ocellatus
      • 1 x Liposarcus multiradiatus
      • 3 x Metynnis argentus
      • 1 x Leporinus fasciatus
    • Building the tank:
      • Background - external printed black background.
      • Substrate - 3mm Coffs Harbour gravel and river sand; 40:50 ratio.
      • Decoration - Driftwood and rockwork - use large rocks that are too heavy for the Oscar to shift and place them on the bottom before the substrate is added so that they can't be undermined..
      • Plants - not necessary.
• Maintenance and Disease....
  • Regular partial water changes and good filtration are essential, as the Oscar is a messy eater and produces a lot of waste.
  • Arrange heaters so that they will not become unattached from the tank glass. Heater guards should be used to protect the heater against breakage.
  • Oscars are known to be quite susceptible to Hole in the Head disease, a condition caused by the protozoan Hexamita.
  • Despite their greedy appetite, Oscars may be prone to problems associated with their diet. The first problem is a general fussiness and refusal to eat food other than the ones they have become accustomed to. This can lead to sulking mood number one. This is easily overcome as long as you are more determined than the Oscar. If the food is ignored, remove it and leave feeding until the next day. This process may need to be repeated for several weeks, but usually succeeds when the fish is hungry enough to eat.
  • More serious is feeding the wrong foods. A diet of solely pellets can lead to intestinal disorders, with the fish resting on the bottom and sometimes with abdominal swelling.
  • Feed a varied diet and feed them more along the lines of their natural food - crustaceans, insects and greens - rather than so much processed food which disintegrates quickly and clouds the water. They love Earthworms - once they get over being frightened of them!
  • Water parameters:
    • pH: acid to neutral (6.0-7.0)
    • Hardness: soft to hard (3-20dH)
    • Temperature: 22-26oC.
• Compatibility....
  • Oscars are predators and can have a mean streak although they will usually get along quite well with fish as large as themselves.
  • Despite their large size, they are quite peaceful. They certainly won't hold their own against the larger aggressive Central American cichlids and are often bullied by these more aggressive fish.
  • The Oscar should be combined in a large community aquarium with other similarly-sized companions.
  • Oscars are ideal kept by themselves or with large Loricarids.

• Breeding....
  • Astronotus ocellatus is a pair-forming open substrate spawner.
  • There are no well defined external differences discernable for male and female Oscars although males tend to be larger and more colourful.
  • Breeding Oscars defend their spawning sites, nest, and young fiercely.
  • Male Oscars may lock jaws in disputes over territory or mate selection which can, if the two are mis-maytched, lead to jaw dislocation.
  • In captivity male and female have been observed to jointly prepare the breeding site.
  • Eggs are adhesive and laid on a flat open surface cleared by the breeding pair.
  • Hatching of eggs is temperature dependent, but typically occurs within 3 to 4 days. After hatching, the wrigglers are moved to a pit that has been dug in the substrate.
  • A single spawning may consist of as many as 1000 - 2000 opaque white eggs. Although they look fungused, they become clear after about 24 hours. If they don't become clear then they are probably either fungused or infertile (females, as with Severums, have been known to pair).
  • The young remain in these pits until they are free-swimming six to seven days later.
  • Sometimes the young may attach themselves to the flanks of the parents.
  • Start feeding with newly hatched Brine Shrimp and commercial fry food.
    Special breeding notes....
  • Breeding usually only takes place in a very large tank.
  • The water must be kept clean and at a warm temperature of 26-30oC. The eggs are susceptible to fungus.
  • Once a pair bonds, they may remain together for over ten years, spawning on a regular basis.

• References....
  Web sites
  Fishbase
  Books
  The Aquarium Fish Handbook (Silverdale Books, 2002)
  Aquarium Fish (Hermes House, 2002)
  Enjoying Cichlids (Cichlid Press, 1993)
  

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ph: (07) 3823 1866