An ion exchange cartridge for a coolant system of a fuel cell stack is provided. The ion exchange cartridge includes a housing with an ion exchange resin disposed therein. The housing includes an inlet and at least one fluid-permeable outlet window configured for coolant to flow therethrough. The ion exchange cartridge is adapted to be removably disposed in the coolant system. An ion exchange cartridge assembly and a coolant tank assembly having the ion exchange cartridge are also provided.