What fish can i keep if i want to get oscars?

if you just got rid of all of them you could only fit 1 oscar in a 55, or 2 juveniles but would need to be upgraded later, oscars should only be kept with other large fish, if a fish can fit into it's mouth, at one point it probably will, a pictus cat only gets arouns 5'' and would be eaten by an oscar as an adult, 3'' isnt big by any means, you already have fish that grow to a foot and oscars get even larger. common species kept with oscars are jack dempsies and common plecos. With the fish you have you could keep the balas (though you need 2 or 3 more) and the pleco but you'd still need a 100+ tank for all that, 2 oscars by themselves would probably need a 100gal at least for them to get full size