Hello,
bichirs are very persistent creatures ... but they do have - like those heroes from the greek (Achilles) and german (Siegfried) mythology a point of massive vulnerability: In this case their slime coat!
Any injuries may cause bacterial infects (it seems that the slime coat of bichirs is acting disinfectant - any analysis are unfortunately absent), with Macrogyrodactylus polypterii (the bad bad bichir-specialized parasite) the most dangerous thing a bichir can happen!
So you have only ONE choice: Seperate these fish!!!
Greetings
Uwe