probably because he is mad that you are in "his territory" male Bettas do that when another is in his territory. like if you put two male Bettas together ( which you don't want to do) they will flare their gills out at each other and end up killing one another... not good. anyway yea they will do the same thing if you put a mirror up to them so the fish can see his self. it can be very amusing! :)
He is probably just showing off at you and protecting his territory. It's the normal behavior of a happy betta.
It may mean he's expecting food and is excited. But more likely he thinks you're threatening and is trying to scare you away.
Could be feeling overly stressed.
No
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.
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.
Betta fish live in rice paddies in places like Thailand. These paddies are miles long but shallow without much current. So the betta fish slowly developed the labyrinth organ which allows the fish to breathe air from the surface rather then use its gills.