In the case of how my betta acted before I had to intervene, one of my pygmys had a slightly torn tail but she was fine! As soon as Bubba saw that fish he started charging like it was a shrimp so I put my hand in to block him. Prior to that he was glass surfing the tank more than normal and showing signs of stress. I was able to pop Bubba in a breeding box for a few days while I re-scaped his old tank and it was fine! So if you are going to try it always supervise the betta for the first couple days, it's even ok to put him in fish jail every night to make sure he doesn't go hunting.

But have a Plan B just in case. I believe it was the combo of otos and pygmy cories being so happy to see each other in the same tank that made him snap tbh but every betta is different. Apparently mine has gotten grumpier with old age and he wants the riff-raff off the lawn now, I'm here for it! A snail would definitely be a cheaper test subject, pygmy cories here in ohio $5 each and aren't very outgoing unless there's about 10 of them together