Purple Dottyback attacking reflection?

I moved my dottyback into a bigger tank and seems like he is attacking his own reflection. Any reason why this might be?

 

When I moved my fish from an acrylic tank to a glass one they tended to attack themselves a lot. The good news is they seemed to stop after a week or two. I think once he realizes "he" is not a threat he will calm down.

 

Yeah I had moved him from an acrylic to glass as well. Maybe he will settle down soon

 

Consider it this way. Glass will naturally act as a one way mirror if there's a huge amount of light on one side and nearly none on the other. The special "one way glass" just has some special coatings applied to make the difference in light levels between the two sides needed to create the effect much lower. Given that we're usually talking about reef tanks with huge amounts of light (think, I have ~250w of T5 on my 55g) on one side, and possibly none or nearly no light on the outside, we're going to experience this effect quite often as reefers. Fish that aren't used to the effect will attack their reflections because of it, especially since the mirror effect gets even more realistic looking with a higher light difference.