The invention is a mixing apparatus for mixing fluids, in particular inks of different colours, the mixing apparatus comprising containers (12a-12d), each adapted for storing a fluid, a tube element (13a-13e), for each container (12a-12d), connected to the container (12a-12d) and having a dispensing end portion at its end being opposite the container (12a-12d), a fluid feed device adapted for dispensing fluid from the containers (12a-12d) via the dispensing end portions, and a mixing space part encasing element (45) having a mixing space part in its inner space, the dispensing end portions of the tube elements (13a-13e) are arranged to extend into the mixing space part, and a filling unit (10) having a base portion (44) and a neck portion (40) adapted for holding the mixing space part encasing element (45), and the base portion (44) and the neck portion (40) are configured to be movable relative to each other, and are adapted for encompassing a container (25) being connectible to the fluid discharge portion. The invention is furthermore a mixing system for mixing fluids comprising a data entry unit (200), a control unit, and the mixing apparatus. The invention is furthermore a fountain pen (100) comprising a container (25) adapted for storing ink which is filled up applying the mixing apparatus.La présente invention concerne un appareil de mélange pour mélanger des fluides, en particulier des encres de différentes couleurs, l'appareil de mélange comprenant des récipients (12a-12d), chacun conçu pour stocker un fluide, un élément tube (13a-13e), pour chaque récipient (12a-12d), raccordé au récipient (12a-12d) et ayant une partie extrémité de distribution à son extrémité opposée au récipient (12a-12d), un dispositif d'alimentation en fluide conçu pour distribuer un fluide à partir des récipients (12a-12d) par l'intermédiaire des parties extrémités de distribution, et un élément d'enveloppement de partie espace de mélange (45) ayant une partie espace de mélange dans so
