Star and the new baby could see each other at first and He was bobbing at her and she waving back. Their tanks are perpendicular to each other, so I put shelf paper on the side of her tank facing him, and that seemed to calm them down.
Both of my girls tanks are right next to each other. I had to put a piece of cardboard between them because Midna didn't want to move or eat and Yaddle kept running all over her side of the glass trying to get to her.
Like I said, They are doing GREAT as they are. It is like a '+' formation, with the cross of the '+' being the girlie's tank with the shelf liner on it. and maybe a foot away from Star's tank... I'll try an upload a rough blueprint of the setup tomorrow after lights on...