Black Cardinal fish aggression
Hello everyone I purchased 3 black cardinal fish about 4 days ago. All seemed fine until tonight, I was watching them when one of them went after the other and grabbed it on its mouth they were like that for a few seconds before it released the other one. I have never seen cardinal fish do this. Can anyone shed some light on what is going on? I thought cardinals were peaceful.
I tried looking them up but I can't find much about them. Thanks in advance.