Diadem PseudochromisHow to Care for Diadem Pseudochromis written by Dave Burr Behavior: The Diadem Pseudochromis packs a punch and may attack fish three times its own size to defend its territory. The pseudochromis species is best kept one per aquarium except in larger aquariums of 300 gallons or more. Diadem Pseudochromis do best in a reef aquarium with plenty of live rock to provide hiding places and create separate territories. The Diadem Pseudochromis should not