Welcome to monster fish keeping. It wouldn't be call monster fish if they didn't show aggressions.
Talking about stress, i just bought 5 bala shark 4"-5" and im worried that they'll become dinner. So what i do is leave the lights on unless its feeding night for the bichirs, after feeding turn the lights on again, lolz.They'll have more room in the bigger tank but then I stress out that they will become a meal. And I do have a larger tank, well a few, that I can set up for these guys. Maybe that will be my best bet. Ugh.. These darn fish are adding to my already stressful life.
Damn thats crazy, is he even letting go of the fin?I think he may be "challenged"... He just sits there with his fin in her mouth.