In addition to the tank size, you will also need to make sure that the tank is properly filtered and heated. Oscars prefer water temperatures between 75-82 degrees Fahrenheit, and the pH should be between 6.0 and 8.0. A good filtration system will help to keep the water clean and free of harmful bacteria.
Oscars are also known to be jumpers, so it is important to make sure that the tank has a tight-fitting lid. They are also messy eaters, so be prepared to vacuum the gravel regularly.
By providing your Oscar with a proper environment, you can help it to live a long and healthy life.