Rats will always fight strange rats because they are naturally territorial. You cannot get non-cagemates to play together outside of the cage normally.
If you plan on introducing them to live together you need to research how to do it. But if you plan on them living alone with playtime together...ain't gonna happen.
If you plan on introducing them to live together you need to research how to do it. But if you plan on them living alone with playtime together...ain't gonna happen.