Common PLecto. Lg usualy no problem. They have the means to defend them selves. In my tropical pond I have 3 Oscars, 3 overgrown bala sharks, ex lg. kissing gouramis, 1 pr lg red parrots, 4 15 plus inch plectos, 4 bullsesye cats. This combo would not work in a tank. The only ones that bother each other are the Oscars, there always to busy chasing each other they don't bother the other fish. Plus they get a lot of crayfish to play with.