An apparatus configured for mixing the contents of one or more fluid containers includes a fluid container support platform configured to hold one or more fluid containers. The fluid container support platform is configured to index the container to one or more specified locations and to be moved in an orbital path about an orbital center independently of the rotation about the central axis of rotation. The apparatus further includes an indexing drive system configured to effect indexing movement of the container support platform and a vortex drive system configured to effect powered orbital movement of the container support platform about the orbital center. An evaporation limiting insert placed within containers reduces exposure of the fluid contents of the container to atmospheric air, thereby reducing susceptibility of the fluid contents to evaporation.