Even though they are still small, they WILL need a bigger tank sooner rather that later. Oscars can be fairly aggressive and 10 gallons is not enough water for the submissive fish to escape the attentions of the dominant one. Oscars are also big waste producers, your dad will probably have a hard time keeping the tank cycled. Also please stop feeding them feeders, they really are not that good for them, (especially if they are goldfish) and the hunting and killing the feeders will only sharpen their aggressive tendencies. At 2 inches, these fish may get along now, but as soon as puberty hits you can expect their personalities to change. As for food, try NLS chichlid pellets, if you can find that where you live.