I have 2 10" Crenicichla cincta females in with a 7" Polypterus delhezi and a 6" Polypterus ornatippinis. The pikes' mouths are big enough to fit the bichirs heads in, but they haven't tried to eat them. When the ornate bichir gets in front of one of the pikes, she'll grab its body in her mouth and push it wherever she wants it to go. I imagine she would try to eat it if it was just a little smaller. However the bichir never has any injuries from these encounters and still swims wherever he wants like he just doesn't care. Bottom line, if neither the bichir nor pike can swallow the other, they'll probably do alright together in neutral pH and moderate hardness water.
