Common Name(s): Oscar, Tiger Oscar, Marble Cichlid, Velvet Cichlid
Scientific Name: Astronotus ocellatus
Adult Size: 12 to 14 inches
Life Expectancy: 10 to 15 years
|Tank Level||Top, mid-dweller|
|Minimum Tank Size||65 gallons|
|pH||6.0 to 7.5|
|Temperature||72 to 77 F (22 to 25 C)|
Origin and Distribution
Like many South American cichlids, the Oscar originates from the Amazon and Orinoco river basins. They are common in the aquarium hobby with most individuals being captive bred.
They are commonly sold in South American markets as a food fish and have been introduced to Asia, Australia and North America. They are labeled a non-native pest species in many US states where fish have been released into the wild.
Colors and Markings
The common Oscar is also known as the Tiger Oscar, a darker brown to light green fish with highlights of red and orange. The color pattern can vary wildly with a characteristic eye spot, or ocelli, on the tail fin. There are albino variations with an all white body with red spots.
Be very careful when selecting tankmates for your oscar. Although they may start out small, many quickly outgrow smaller tankmates and then consume them. These are semi-aggressive cichlids who do not play well with many community fish. Remember, when choosing compatible cichlid species, make sure you select fish from the same region. Even though there are many varieties of cichlids, their origin will dictate what water quality parameters are best for them. Since oscars are South American, be sure to stick to other South American varieties.
Oscar Habitat and Care
Oscars are notorious redecorators. Do not get attached to anything in the aquarium and expect your fish to move everything. This is especially true of live plants with roots. Oscars will dig up plants, overturn rocks and toss sticks aside. It's just in their nature and there is not much you can do to deter rearranging behavior.
This aggressive nature towards their tank decor may turn against filtration and other life support items you have in their tank, such as powerheads and heaters. Oscars have been known to break these items, even if you try to be sneaky about hiding them. The best solution for many destructive oscar tanks is to incorporate a sump. In doing so, you can move all of your life support equipment out of the main tank and away from your fish.
Oscars are sticklers for good water chemistry, so it is vital that you keep up with your regular maintenance and check your water chemistry regularly. They are more susceptible to Head and Lateral Line Erosion, also known as Hole-In-The-Head disease, which can occur when fish are chronically stressed.
Oscar Diet and Feeding
Oscars are serious carnivores who will prey upon smaller, more docile fish in their tank. It is critical to select suitable tankmates who will not look or act too tasty.
As with most pet fish species, a well-rounded diet will consist of a pelleted cichlid diet and meaty supplements. There are many pelleted cichlid diets that are good for a wide variety of cichlid diets, carnivores included. Additional protein-rich foods to give your oscar include bloodworms, tubifex worms, frozen krill and other larger frozen diets. Although some recommend feeding your oscar live foods, this should be avoided in order to limit the spread of disease into your system and potentially overpopulating your tank.
There is a very small external difference between male and female oscars. You will need to safely catch and handle your fish, and flip them upside down to examine their urogenital openings. Oscar females will have one larger hole, which is the opening for their eggs. Oscar males will have holes of similar size. If they are not reproductively mature, the holes will look the same size regardless of their sex.
Breeding the Oscar
Even if you have one male and female oscar, they may not be interested in breeding. Oscars can be picky when it comes to selecting a mate. If your fish are not initially interested, do not despair and try moving them back to their main tank, incorporating different decor items to the breeding tank or getting a larger breeding tank.
It is recommended to breed your oscars in a separate tank away from other fish, in a 100 gallon tank or larger. Temperature is critical to induce spawning, and should be warmer than their usual tank, 79 to 86 F (26 to 30 C). You will need some rocky substrate for the fish to lay their eggs. The female will lay between 1,000-2,000 eggs which the male will then swim over to fertilize. The eggs and fry will be guarded by their parents and should remain in the breeding tank until they can fend for themselves.
More Pet Fish Species and Further Research
If you like oscars and are interested in some similar fish species, read up on:
Check out additional fish species profiles for more information on other freshwater fish.