I caught my female betta attacking a neon, but it may have been sick to start with? it was still alive, it really nailed it then the fish died and it got consumed by the clowns eventually...definitely keeping a weary eye now. I've kept just a male in the past with a bunch of neons and other tetras with no problem on the other hand, oh one thing is if the betta is red, and you feed bloodworms, be careful as the tetras will attack the betta's fins assuming they're bloodworms.