I have a male and female red empress. Mine are pretty peaceful except when they want to spawn and then the male chases but wont harm the others, he is obsessed with his female for a day or two then reverts back to normal till next time. I do have them in a over sized extra large tank though, a smaller tank like a 55 or 75 might have more issues than i have in a 7 foot 265 gallon tank.
