When my Betta, Fred, first met his tank makes, he did pick on them somewhat, but mostly just displayed to them. What I did was to set up the plants in the tank so that Fred did not have an unobstructed line of sight through the entire tank, which allowed the other fish to swim behind the plants to hide. It worked pretty well for me and Fred soon got used to seeing the other fish but without having an option to pick on them continually.