I just watched a youtube video showing a bunch of Betta Fish together with hardly any issues. It has been said time and time again that these jokers will go after each other (the males). What am I missing?
Betta sororities with only females and a large tank is possible, and the young can be kept together for a while. Also, most bettas can easily and peacefully be kept together if it's a species other than betta splendis. I'm not experienced enough to tell you which one is happening in the video though, but I don't think I saw any males.
Betta splendens is almost the only species of betta in which the males can't be kept together. With female betta splendens, sororities are a possibility.
With the video, my guess is that they were all just very long-finned females. Most are probably not even in an established sorority, given tank size and the level of stress and aggression those fish were displaying.
I'm no fish behaviourist, but my guess would be this is a sorority of females who were raised together. They all look very similar, they might be siblings who've been together since they hatched.
As was mentioned above, large numbers can also lead to dispersed aggression. I know horses better than fish and this is a known social feature in horses: having more in a group makes it less likely individuals will have one-on-one aggressive behaviours.
I could put my 2 males and 13 females into a small tank and i bet i could make a 10 minute video but what would it prove. Would make a pretty convincing video however. Long term i think i will leave them in the 75. There was more chasing and niping in that short video than i observe in a week in my setup. The parts of the video with a whole bunch of them look like fry so thats not surprising but the peace will not last.