I guess he can. i've moved him into a new 5 gal. tank 2 weeks ago he was upset for a while but now he's back to his old self, except he's flareing his gills and it only started today. so if that's all it is, I don't have to worry?
A flaring betta is perfectly normal. That's just their way of letting you know (or the betta they see in the reflection) that the "enemy" needs to get away from their territory. As long as your water parameters are on target, I wouldn't be concerned.
Welcome, it sounds like he's settled in and is claiming his territory from himself lol! Flaring is fine, one of mines seems to think whenever he does it, it triggers a food release! When I open the lid and he sees my hand, he flares, then he gets food. The reason the lid is open in the first place is to feed, he does not realise this!
Wait till your boy blows a bubble nest, he's all grown up then!!
Bettas are great I'm so addicted to them cause they are so gorgeous!!!! Hes absolutely normal, hes showing himself whos boss, lol. I have a female who flares at her reflection in the glass all the time. I didnt know the females flared until recently so it was a surprise to me too!!!!! My male flares at the little Budda statue I have in his tank.