Name: Astronotus ocellatus
Origin: South America
Oscars grow very rapidly, as much as 3 cm per month if well fed, sometimes more. They tend to slow down at 18-20 cm, but will eventually reach 30 cm. Stories of 40 cm, although rare, are not impossible. They do not need to be kept isolated - some company tends to result in a livelier and happier fish. But don't mix them with aggressive cichlids such as the Jack Dempseys or Convicts, unless the tank is very large (600+ liters). Can be kept with Severums and other big peaceful cichlids. Put some 'dither' fish with them, such as Giant Danios or Tin Foil Barbs - they keep the Oscars active and eat a lot of left over food.
Minimum tank for one specimen would be 120x45x45 cm (250 L, and in my opinion a tank this size if well maintained can also house 'dither' fish) and an external and internal filter highly recommended. Bright lighting tends to increase aggression. Avoid sharp decorations, Oscars are forever banging into stuff and damage easily, although they heal remarkably quickly, especially if water quality is maintained. Keep the water well filtered and clean - by doing so your Oscar will rarely (if ever) get a disease and you will save yourself a lot of hassle in the long run. Hole in the Head Disease (HITH) can be prevented by feeding a varied diet and maintaining good water quality. They are not sensitive to water chemistry as long as extremes are avoided. They love and thrive in clean fresh water (obviously dechlorinated). Ideal temp of 26-27°C. Change 20% minimum a week, and 50% maximum a week - any more and you may disturb the good bacteria present in your filter and cause more problems with your biological filter.
Feed them a varied diet - prawns, earthworms, bloodworm, shrimp, bugs, etc, plus a good quality cichlid pellet. Experiment with different foods, some foods tend to be wafted out all over the tank, others gulped down in one. You can to some extent control the pollution with certain foods, e.g., some pellets are gulped down, other brands are wafted out, trial and error. Do not feed feeder goldfish, unfortunately the only purpose they serve is to entertain. They are high in fat and unless you quarantine them they could carry disease. This is very important - feed a big juicy earthworm instead - just as much fun and very high in easily digestible protein.
Summary: Unfortunately a highly abused fish that rarely is given the space and care it needs to THRIVE. They are highly intelligent fish, that will bond with people and other fish alike. They are easy to keep due to their hardiness, however this often means they are subjected to poor conditions. Caring for them properly is more of a challenge, and anyone thinking of keeping them should take into account their requirements, so before you buy an Oscar - do some research! Enjoy!
A beautiful and personable fish, they are easily bought very inexpensively at a small size, but the eventual size of the fish should be considered before purchase. A 100 gallon tank would be considered to be a minimum size for a pair of these fish. A high-volume filter is also a necessity, as the fish are messy eaters, and regardless of tank size, regular water changes should be performed in order to keep the fish in good health. Meaty foods, especially live foods are recommended, but if feeding goldfish or other "feeders", be careful not to introduce disease to the tank.
Oscars can be hand fed and I think they like gold fish better than pellets. I also know that it is best that you have a lid on their tank, because I had some that made a sky dive unto the floor and I made it there two weeks too late!
Oscars are excellent predators, and they do like to be hand fed, only make sure you have ten fingers when the feeding is done. When you add fishes to the aquarium, make sure they are quick, so they can get out of harm way in time.
I had an Oscar that I just loved! He would only eat goldfish....and any other fish! When I first bought him, he was a little baby, but soon I realized the little baby wasn't a baby anymore so I had to buy a 20 gallon tank! When I first bought him, he would eat nothing but flakes, but one day when I woke up, I realized that I was missing a fish, the Oscar had part of the fish in his mouth! I was so mad but I looked at him and he gave me a look like..."well I was hungry"! I love Oscars and one of these days I'm going to buy another one!
I used to have a large, male tiger oscar. He was large in size, but his personality was even more immense! In between feedings of cichlid gold and goldfish, I would feed him large crayfish. They would raise their claws in defense, but he would dart at them so fast that their claws would pop off and their body would be stuffed in the oscar's always hungry mouth. You could hear the crunching through the glass!