A replaceable ink tank for an ink cartridge used in a bubble jet printer comprises a container formed by two side walls providing major surfaces of the container, and back, front, top and bottom walls. At least one ink supply port is provided in the bottom wall of container and is disposed for supplying ink from at least one ink chamber in the container to a corresponding ink tapping pipe in the ink cartridge. The container is configured for insertion into an opening in the top and front of the ink cartridge with the bottom wall of the container facing downward and a back wall facing a back wall of the ink cartridge, the container being constructed for engaging a camming shoe located at the back inside of a top wall of the cartridge and securing the container in place in the ink cartridge with the ink supply port connecting with the corresponding ink tapping pipe.