i just bought a lovely little red betta, he has a nice tank swims a lot, i feed he and he eats it. but every time my parents come in he flares up and starts going for them and then hides, whats up with him?
Some Betta's can be very aggressive your seems to be one of them. He is most likely scared of them and think they are threat and will hurt them. They flare so it makes them look larger and to try to scare of predators to them. Mine used to do the same think but now he is less aggressive and is with Neons and Clodufish. So he has cane a long way from when he was aggressive and flared like yours.
I suggest you wait a week and see if he stop flaring at your Parents.
Blue.biso Any fish can learn to be less territorial you just need to take the time.
Hope this helps!
Good Luck!