I thought my baby was a girl. But the other day I was looking at her and I thought her tail was getting longer and maybe it's a boy. Today I went to do the water change on the tank and there was a huge bubble nest.
The females can have fairly long fins, but it'll be in proportion to their bodies. I've got one who has very long fins for a female, but they're still much shorter than a male's would be, and they're very round. They don't have the "drag" that most of the males have (except plakats) unless they're actively fanned out.
Also, females will have an egg spot, but I've read that it can be difficult to tell on some females. If you post a picture, I'd bet that someone on here can ID her/him for you, gender-wise. :)
Again, +1 on female nests being disorganized, and a bump on a picture ID.
Penelope is FOR CERTAIN a female, but she blows nests, and they are all over the place. I think she does it to intimidate the other females in the sorority. Is the baby in question within sight of other fish?
The baby in question is in a shared tank with a male. The bubble nest was huge. Not disorganized at all. It was nearly an inch in height as well. It was taller and better constructed than any nest the male in the tank with her has ever built. I wish I had gotten a picture. It was destroyed with the water change and I keep checking the tank to see if the baby has started a new one.
Yes females can build bubble nest, I had 5 at 1 time that built nest & most of them were just as good as my boys nest.
I have 1 female now who builds her own nest, then releases her eggs and fills it herself! I know it's all done by here because there is no other fish with her. I started having problems with my sorority (not fish fighting) and removed all my ladies to clean things up & try and fix the water quality issues. The day after I pulled them all Venus had this nest built & filled. I watched her take eggs out & clean them, then put them back in. If one fell she chased it & put it back in. Now, her nest didn't stay together well, parts kept drifting off, but she'd just take the eggs and add them back to the main part. I left her be with her eggs for a couple days to see what would happen and then did a water change. The next morning there was another nest, smaller & with fewer eggs, but there all the same. This betta is 100% female, but with nests & eggs does the mans job as well.