A flexible tank (10, 110) for transporting fluids in a transportation container (12) is described, the flexible tank (10, 110) defining a tank (10) volume for containing a fluid. The flexible tank (10, 110) comprises at least one mixing member (146, 46) enclosing a fluid pathway (160, 60) extending across an interior surface (144, 44) of the flexible tank (10, 110), the flexible tank (10, 110) further comprising at least one inlet valve (140, 40) configured to allow the passage of fluid from outside said flexible tank (10, 110) into said fluid pathway (160, 60). The mixing member (146, 46) further comprises at least one aperture (154) such that the inlet valve (140, 40) is in fluid communication with the tank (10) volume via the fluid pathway (160, 60). An intermodal container (12) comprising the flexible tank (10, 110) and a method of mixing a fluid with the tank (10) are also disclosed.