Yes the bb is different. One is adapted to live in saltier conditions so moving it to freshwater or vice versa will kill it unfortunately.
i tested my water for ammonia/trites/trates and im spiking even though i kept my filters cycled buy putting them on another freshwater tank. im glad i took the advice to let my saltwater tank cycle before adding any fish.
My 55 went from fresh, to salt, to fresh, to salt, then became a turtle tank, and now fresh again. Granted I have had it for 15 years, but all I did to clean it was use super super hot water and rinse very well.