So I'm guessing the tank is 4 ft. in length, correct?
Either way, you'll need to find new homes for 2 of the oscars. Even with only one full-grown (and yes, I realize yours aren't full-grown yet, but they will be before you know it!) oscar in that tank, you'd be looking at having to do at least two large (50%+) water changes...possibly more...per week to keep nitrAtes at safe levels (at or below 20 PPM). For this reason, the general recommendation for keeping a single oscar is no less than 55 gal. Also, if you attempt to keep more than one oscar in that tank long-term, you will almost certainly be faced with a scenario where the oscars kill each other.
BV