Methods and systems for monitoring fluid levels and electrolyte levels used in a dialysis machine. A receptacle, configured to receive a container, comprises a plurality of curved side panels and a base to form a cylindrical shaped cavity for receiving a container. Each panel includes a conductive material on its inner surface and, optionally, a shielding on its outer surface. An electronics component housed within, or near, the receptacle drives the capacitive process and interprets generated data to determine fluid levels and compositions. An alternate receptacle includes one or two coils wrapped about the container and uses induction to determine fluid level.