Every once in a while, my betta will chase my tetras around a little. I know that when the tetras are doing it, they're playing around. I wanted to know if bettas will try to play too, or if I should worry that it's trying to hurt the tetras.
In my experience, bettas don't play nice with other fish. They don't even play nice with their own kind. I had my betta in a community tank but he would chase other fish and flare at them or nip at them so I had to remove him from the tank .all the female bettas I tried keeping were far too aggressive for a community .they are best kept alone .
I'm going to go against the grain here and say that I honestly wouldn't discount the idea that your betta is just messing around. I had a gudgeon in my large tank, and he was the grumpiest fish ever. He would challenge for dominance every fish in the tank, even though some of them were twice his size. Well, after he got knocked into his place, his hobby seemed to be tetra chasing. He would just chase them off for a few inches, and I know that he was doing it because he was grumpy, but it was also just harmless chasing. I honestly think he enjoyed it, he was just glad to be able to be bigger than someone. I think it depends on how your betta chases them. Does he swim super fast after them and try to bite them, or does he just sort of swim at them for a couple of inches then ignore them? Has he done any damage, and does it look like he might do some damage? I'd keep a really close eye on things to see if they get any worse, but I don't think you have to be super worried about it.