You can pick my brain I keep these:
-55g tank with assorted tropical community fish; platies, tetras, iridescent sharks. And a few small channel cats that are bound for a larger tank soon.
-55g tank if assorted fancy goldfish, with a giant comet GF.
-120g Oscar tank with 2.3 clawed frogs, a few large plecos, an algae eater and a Livingstoni. This tank is a delicate balance and it works with 2 nonagressive Oscars; most are pretty aggro and not good for this type of setup.
I definately do not advocate keeping fish together that are fighting It is not for our entertainment that they are injuring themselves. I have never kept RDs but I think that you are along the right track, planning having several tanks if they can't get along.