Bettas generally flare out their gills to look bigger than they are, with one of two primary goals. First, as a courtship moves ("hey, I'm worth looking at!") or as an aggression/dominance expression in order to intimidate or stake our territory. They may even do it in the absence of other fish, if they are used to being fed by humans and want to get your attention...and your food. It is perfectly normal. It is showing off, probably because it saw it's own reflection or another male, or female, and is "flirting" with her.
Not with many fish, although holding a mirror to a betta will cause it to flare its gills as it will think its reflection is competition
It means he hates you. Bettas flare their gills out when they're trying to scare another betta away, or to impress a female with how large he is.
When betta fish flare their gills, it usually means that they want to show off; either to other fish, or to their owner. Sometimes, if you scare your betta fish, they will flare their gills at you just to let you know that they aren't afraid of you. if your betta fish flares their gills all of the time, you may just have a very aggressive fish.
Bettas flare to scare other fish from their territories or to attract a female.
yes what about the betta fish and mirror?? will it flare or just ignore it?please give details
Yes, the "red thing" is actually called a membrane. Bettas will flare out their gills and membranes when he is feeling threatened, especially by another Betta fish.
stress?
Mainly for territorial and mating purposes. Bettas are very territorial and will attack any fish with bright colors and large fins. Especially other Bettas. Bettas flare when threatened by opening out their fins and extending a 'beard' from under their gills.
Of course they can all fish have gills which allow them to breath in water.
They're territorial fish. They flare up to make themselves look larger. In doing this, they may scare away possible threats to themselves and their territory.
Simple. Betta fish are territorial. They see movement, and color as a threat. They will do this even to the females until maybe mating season.
Some bettas just have dark gills, even the white ones.