An ink tank cartridge for use in an ink jet recorder has a container having exterior walls, a porous member is stored in the container, an ink supply port that extends through one of the exterior walls of the body to supply ink to the exterior of the cartridge, and a packing member, disposed within the ink supply port and having an opening therethrough and a rib formed on a upper surface. A pressing member may be provided to bias the packing member against an inner surface of the ink supply port. The ink tank cartridge can be assembled to limit the occurrence of air bubbles in the tank.