Union orings?

[Johnd651]

So, new to me tank, and I lost some orings during transport. At this point I think I will replace all of the union orings since it's not a big difference in cost.

The oring shop recommended buna n 70 duro for saltwater application. Is this correct?

 

[Kingsley_Reef]

I believe the EPDM o rings are better then buna