Oscar (Astronotus spp.)

Common Name:

Oscar.

Scientific Name:

Astronotus spp.

Family:

Cichlidae.

Class:

South American Cichlid.

Distribution:

They're found in the Amazon Basin in the nations of Peru, Colombia, and Brazil.

Diet:

While it can be considered fun to see an Oscar engulf a feeder goldfish, this is not a good idea. Goldfish are high in chemicals which may inhibit the growth of Oscars as well as their absorption of essential nutrients. Any fish that has lower fat content may be an acceptable food for an Oscar, but it is necessary to quarantine any live fish to make sure that the feeder will not spread disease to your 'aquatic puppy'. For those who cringe at the prospect of feeding another fish to their Oscar, there are other live foods which will make Oscars very happy. Crayfish are quickly dispatched by Oscars, but their shells and assorted body parts will hurt the tank's balance. Marine fish fillets are also greedily accepted. The old diet of beef heart mashed up will suffice, though there are some serious nutritional deficiencies in Oscars fed beef heart exclusively. Plus, it is messy and there are better options. There are also cichlid pellets and 'Oscar growth formula' foods commercially available. These may form the basis of a complete diet for your Oscar, but live foods or commercially prepared versions thereof are always welcome supplements to such a diet. Fortunately, Oscars eat greedily and will take almost anything offered to them as food.

Water Temperature:

In the wild, they live in water with temperatures between 74 and 80 degrees Fahrenheit, so that would be the recommendation for captivity as well.

Water Chemistry:

Yes, definitely. Oscars are easily among the top few fish to show signs of Hole-in-the-Head disease (neuromast pitting) because of their popularity and the poor care given to them by the unitiated. Heavily filtering the water and regularly changing it will help stave off this insidious disorder. Larger tanks will allow the water quality to slowly degrade for a slightly longer time than in a smaller tank but, make no mistake, the degradation of water quality happens very quickly with a 14" fish that eats everything in sight and begs for food constantly. The water quality parameters in which these fish are found in the wild are pretty varied: they live in pHs between 6.0 and 8.0 as well as dH levels from 5.0 and 19.0, so they're not extremely picky about water quality, especially in captivity. Consistent pH and hardnesses are the key.

Life Span:

Approx 12-15 years.

Housing:

90 gallons for a single specimen. A mature pair will need something on the order of 125-135 gallons at a minimum.

Sexing:

Don't you hate isomorphism? Cichlids will pair off if you buy a sufficient number of juveniles; usually six guarantees near 100% odds of a pair forming. Now, unfortunately, two females will sometimes show signs of having paired off and lay eggs together. A series of infertile clutches may convince the keeper that they have a pair of females. Some swear by the so-called 'one-hole, two-hole' method of sexing the fish by a process similar to venting. This doesn't always work and can be stressful on your fish, so the recommendation would be to learn this method of sexing from someone who is experienced in doing so and lives nearby. There may be fin anomalies that show sexual dimorphisms, but none of the major publications which I have read even touch upon this possibility.

Breeding:

The pair needs to be conditioned for spawning via the feeding of live foods. The pair may test each other's strength via a lip-locking ritual. If both pass the ritual, they may start to clean off rocks in the tank. It is a good idea to provide them with flat pieces of slate/shale on which they can lay eggs. Once the rock is clean, they will start to lay eggs and fertilize them. Unlike many other fish, the Oscars will actually care for their eggs and will take on the role of protector and anti-fungal agent for the roe. They also practice brood care once the babies have hatched, so it is safe to leave them with mom and dad for a while; up until they get to be four weeks old. Once they attain the size of 1", they are considered saleable. A couple of notes on breeding and subsequent rearing: The eggs look like normal fish eggs but a little larger than those of the other tropical standbys in the hobby, and they're coloured an opaque, milky white (which look similar to fungused eggs of other species). The fry need no special food as the parents will grind up their normal food for the babies. They will, however, need regular feedings once transferred to their grow-out containers.

Behaviour:

These are the prototypical 'aquatic puppies'. The Oscar is famous for showing off for any humans that enter its room, bobbing up and down, waving its head back and forth, and generally begging for food. It's hard to turn one down in such a request! These fish show true intelligence and they methodically search their tanks for food and can even learn rudimentary tricks. Their awareness of surroundings and joie de vivre endear them to all. Their reputation for being aggressive is overblown. They will eat what tankmates they can and may guard their territories, but they won't actively destroy tankmates like some other fish are known to do. They will, however, rearrange whatever furniture they may be provided. They quickly dispatch plants and are inveterate diggers. These facts should be considered when designing an Oscar tank!

Miscellaneous:

I've even seen the Oscar listed as a Cichlasomine fish, but it is obvious to most (if not all but a few inveterate lumpers) taxonomists that this is not the case. I have listed the Oscar here as a complex of species because that's Axelrod's point of view and I will not debate with him. By this view, though, most pet Oscars are hybrids or must be viewed as such. One final taxonomic note on the O: It is the reason why the genus Acara is rendered unusable. Acara crassipinnis, a junior synonym for either Astronotus ocellatus (if you regard Astronotus as a monotypic genus) or As. crassipinnis if you share Axelrod's view. Why does Axelrod split the As. orbicularis from As. ocellatus? Quite simply, they live in different biotopes in the wild and their corresponding juveniles are morphologically different from each other. It would seem to me that this would at least merit subspecific status for As. orbicularis

Photo Credit:

Photos supplied courtesy and ^©Chris78Corvette.