I used to have 8 RBP in 240 gal (6ft x 3ft tank), which I grew from inch-lings to mature adults. They didn't swim much, just kind of hovered in the middle of the tank. When I walked in the room they would all "twitch" a little and come forward for food. It was very entertaining to watch their feeding habits.
I had them with an Oscar, Polleni, Jaguar cichlid, convicts and some clown loaches. The RBP were added in last so they grew up with the all my fish. No one messed with them, so they didn't mess with anyone. Until one day the Jag started getting aggressive and lost his entire bottom jaw trying to lip lock with one.
I had a friend who used to keep Pangasius, one day his tank broke and no one had a big enough tank to hold them expect me. I warned him that although they are peaceful with my other fish, they may not be to new comers whom they didn't grow up with.
so I rearranged the tank, turned off the lights (this was at night so the room was dark) and introduced the two pangasius. They seemed fine and not so interested, so I went to put the buckets outside, came back inside and the pangasius were gone. Literally stripped to the bone. There was only a head of one left, and the other had a head and half a spine which was twitching. My Oscar, polleni, convicts and loaches were all huddled, squished in one corner together, whilst the RBP had their usual, casual, chilled position. Hovering in the middle of the tank.
