Hi FishFancier,
Well, just as Chuck said, they grow fast, so do frequent water changes. And plan to upgrade your tank when your fish gets 6" or even sooner if you can afford it. I recommend you go to a 55gallon *at least* and get another oscar, preferably opposite sex. Like Chuck said, most people find to 70 to 90 Gallons to be a good compromise between oscar well being and their pocketbook. Bigger is always better though....
Joe
www.cichlidfish.com