I own 2 young Bettas of same look and appearance. One of them keeps making bubbles, so its obiously a male. The other doesn't ever flare up or make bubbles. I cant seem to identify its gender. Anyways when I put them together even after the other has made bubbles, it just abuses the crap out of the other one (that doesn't flare). I believe they are siblings.
I'm considering going out and finding a female betta seller, so i know 100% the gender. I did rescue a Betta recently i was told was female but she's 5 years old (and massive... size of a small gold fish) it has some health issues so i wont risk breeding it.
I also have another 4th betta which has very long fins. I believe to be male as it flares up and attacks snails all the time.
I'm really hoping i can one day have a successful breeding of my obvious male betta. He's just always making bubble nests but unfortunately he's very aggressive so not sure if thats a factor?