No, I have no serious problem with several specimens of the same species or different ones together, but I will introduce them again after my holding them in a small bucket for some ten minutes with aeration.
But some of these will sometimes have a trouble with fighting (actually they exhibit an unbeliebable coloration!), and it will usually appear soon after introduction. I will save the weaker one and put it in a smaller box or another tank for recovery for several days.
Another male specimen in display.