Originally Posted by 1fish2fish
They can't "change" gender. A female will not suddenly lose ovaries and become a male. Some fry are just slow developers and may not show male/female tendencies until later in development.
I respectfully disagree.
Given the right conditions, female bettas are capable of changing to male. Of course it does not happen suddenly. According to my source, if a female has spawned, she will always be female. Of course there are some males that are just slow developers, or maybe not? Anyway, I personally have seen cellophane fish with very visible ovaries that matured later into fully functioning males. I thought I was going crazy until I asked someone at a show who would know more than me about bettas changing sex. Many types of fish are capable of changing their gender. It is not unusual at all for fish. For example clownfish can change from male to female and Centropyge angelfish can change from female to male. Anyway, yes female bettas may be capable of changing to male just like many other types fish.