Well oscars personality is like a pig its eats a lot and make dirt a lot.
So you need to water change weekly 50% and have good filtration.
Eating a healthy diet is good like bloodworms, hikari staple or bio gold, recommended is New life spectrum ..
Have fun with your oscar.
and 1 more thing they'll grow very big and fat so when they are adults 75gallon for single and 100g + for more oscars
keep with ur little pussy cat, they will become close friends
put it in water