I've got 2 osacrs that are starting to show signs of hole in the head. I had 2 others that I just got rid of because of excessive fighting. About 6 hours after I got the 2 out I noticed it. Figure it's stress from the fighting or from the fight the 2 put up coming out of the tank. Anyways, I started noticing my arowana has some holes on his lower jaw that I don't believe were there before. Maybe they were and I'm just getting overly concerned. Anyone ever seen an arowana get hole in the head? Water parameters have not changed at all in 3 months if you're about to ask.