Hi gonzo! welcome to fishlore!! I moved your thread to its own area so you might have more members able to answer yours specifically instead of confusing with the original posters questions ..
in a 50 gal tank, you are pretty maxed out with just the bala's..they get to over a foot and really bang around a tank the bigger they get...its recommended a 55 gal for one bala

....if you plan to keep them, I wouldnt add anything else..if you can get a bigger tank or are planning on rehoming them, you still probably have the max of dollars at 4 for the 55 gal..lets see what some other members might have for suggestions. ...good luck!