Will a Betta fish really fight with itself in a mirror?

Answer by  Aqua (130)

A Betta would not outright attack an image he perceives as another betta, but he would try to impress the other Betta by flaring all his fins and tail. A mirror is not always necessary, sometimes his reflection on the inside of the glass can set him off, too.

Answer by  okcmouseketeer (779)

Most beta fish will not really "attack" their image, but will puff up into the aggresive posture and swim around aggresively. Each time they do this, it can raise stress hormone levels, just like fights in human's release hormones. If only done a few times, it would be fine, but doing this alot could cause problems for the fish.