ok so both of my endlicheri bichirs are about 6" nose to fin. i got both of them at the same time and both were put in at the same time. i've never had any problems with them before but tonight i came home from the LFS and noticed one bit the others face/whole head and wouldnt let go. they are currently in a 72 gallon bow front tank. why is one so aggressive? this is the first time i've noticed this aggression. they are also housed with 1 rope/reed fish and 3 plecos one common, one tiger, and one candy. have my bichirs already outgrown my tank?