My betta, Ciel, has never flared at a mirror, but when I walk in and take a look at him he likes to flare at him. Most of the time it's not even a full flare. The other day I walked in and looked at him. He swam around his plant turned to face me and gave me a big flare. I have never seen him flare that much before and haven't seen him do it again ether. Since Ciel doesn't flare at mirrors I don't think I could teach him to flare on command, but I have been trying to teach him to swim through a hoop.