Thanks. I still miss him every day.
Well, if you can see the dark blue one in the video, he was twice the size of my other boys, and he got across the divider and ripped half the fins off of my Donovan. At the moment I only have Donovan and Emerson in there, and they don't fight at all, even though Donovan is a showy little guy. Just be careful that you position your divider right so that they don't get across. I accidentally bumped it a bit a few days ago, and I found Emerson swimming around on Donovan's side. They didn't attack each other though.

And if they are sitting at the divider flaring, you can usually fix that by putting lots of plants against one side of the divider to distort the view.