I had my dovii (15") in with a black shark (13") until he grabbed it and bashed it against the glass almost killing it. So he got put into a 6x20x20 with a jardini thats also turned into a killer. they have been together for over a month and not so much as a tuffle.
dovii pair 240 gal no tankmates.
dovii pair 180 gal no tank mates
6 black gorillas umbee growouts 4-6 inches no tank mates. each in its own 50 gal.
single rio mag 75 gal. no tankmates.