My Suggestion would be to start saving your money. The fish you have really need a tank 4-5 times the size of the one you've got.
I was in your shoes when I first started keeping tropical fish. I had a 55 gallon (US) starter kit and it just looked empty. So over the course of about a month I bought 2 oscars, 2 Jack Dempseys, 5 silver dollars, 1 snow king pleco, 1 pimedella catfish, 1 channel catfish, 1 blue gourami, and 1 red devil. Everything was fine for the first couple months. But I got to a point were my water was always cloudy. So bought another filter. I eventually had the replace both of them with better filters. It got to a point where I was constantly doing water changes. Then I started having issues with waterborne algae. Then I had to do constant water changes just to keep my house from smelling like a sewer. Finally, during one of my weekly 50% water changes my now 18 inch long channel catfish lost his mind and basically commited suicide by smashing his face into every possible surface within the aquarium. That was the tipping point, 18 months after starting my tropical fish hobby I was forced to either part with my fish, or get a bigger tank. I chose the latter. Actually, I got one big tank and a few other smaller ones.
I know that getting new fish is a urge that's hard to resist. I love it when I get to go out and get something cool, something that I've never had, something new to discover and learn about and fascinate over. Just don't lose sight of you Oscar. He's got a lot of development ahead of him; new behaviors, new interests, new tastes in foods. If you ever want to see all the cool things that your fish will grow up to be. You need to get him better housing so that he has a chance to show all of them to you.
hi ,
