Hello,
in one of my tanks the one and only species that is a bit aggressive is Polypterus delhezi - the two males are biting each other without hurting ... i think there is no problem.
When my P.senegalus are doing courtship the male chases the other male away - they do this in change ...
I've read in many aquaristic-orientated books about aggressions between bichirs - in majority of cases the same words were used. It seems to me that the autors transcribed this of each other. This is usual in many other facts belonging to bichirs ...
Greetings
Uwe