I have never really made any effort to get my fish to flare I've focused on talking to them and forming a "relationship". So today I wanted to take some pictures and I decided to get a mirror. I had two reactions one fish ran behind some leaves and was watching me when I put the mirror down he came back out. The other two ignored the mirror swam past it and were trying to get my attention. I had fed them recently they should have been full. Either way they had no interest that fish in the mirror. They just kept looking for me and wiggling around.
On other occasions some of my fish put on a little bit of show when I come around but I really don't think it's defensive they are hoping I will feed them and are trying to get my attention. I have read that some bettas will flare a bit to get their human "feeders" attention. I found it funny that they really don't care about the mirror.