I have a male living with 5 female bettas in a 20G long. Granted it was not intentional. I picked up 4 very young females one one just happened to of been mislabeled by petco. he tends to get a little more nippy after I trim back my plants since it creates more open space but nothing out of the ordinary. They have been together for about a year now.
He looked female to me
When I first put them together in a 10G - they were all pretty young.
when I first started to suspect he wasn't a female - his fins kept growing
I waited for 20 minutes one day to get a pic of them together. It looks like the white one is ready to smack him, the red one caught him with his mistress and the baby is like "are you my daddy?" I don't know where the other 2 were hiding
They don't LOOK stressed, do they?? it does look like he is about to be tail smacked though