They can be a little nasty with their own kind, but other fish the males will simply chase out of their territory. Some individuals can get nippy, but that might be if there aren't enough of their kind in the tank.
To be honest, the last time I kept these in a community tank was 1967. I normally put them in a species tank for breeding these days.
I would say 2-3 males and 2-3 females per male. The species is territorial, males protect a patch of plants usually and breed with the females when they come around. They are more vegetarian than your tropical Killifish, and are known to eat hair algae.
Why was a Killifish thread moved to the Cyprinids?
No Idea, I'm hesitant to try them if they are aggressive though, dont want my bottom dwellers beat up if they get close. when I go to actually do it I may change my mind if I learn more later Thanks though! I know a ratio of 1:3 though like most gouramis etc