The entire purpose around maintaining a fish aquarium with Oscars is to watch them grow into large carnivorous fish. While these fish grow aggressively on their own, there are tried and true ways to increase an Oscars size more quickly. This easy feat takes a little care to accomplish.
Feed often. You will want to feed your Oscar's every two to three hours. If you are worried about them not being hungry, an Oscar only has a memory of 13 seconds. He will never remember he just ate a meal.
Choose the right food. There are specific foods on the market designed to make your Oscar grow larger. Using these dry foods in combination with fresh or frozen live foods like shrimp and blood worms will cause enormous weight gain.
Clean up after Oscar. With the increased food intake there is bound to be additional output. Your Oscar will dirty the cage quite often. In order to keep the aquarium environment balanced with healthy bacteria, make sure not to complete a water change too often.