Dependig on the size of the tank your Osacr is in , i would get a few more Silver Dollars and put a largeish school of about 8+ SD'in the tank ( more the better ) .
Silver Dollar are Schooling fish and do better in large Schools rather than a Single fish so if you can get a few more i would deffently put your SD' in with your Oscar .
If it's anything less then a 1000 gal pond it wont be big enough for that pacu. I say eat the pacu, and upgrade to a 120 or larger for the other fish, and get a school of a dozen SD. That's just my opinion.