Bosch Water Dispenser Produces Moldy Stuff

Despite trying various water brands, my Bosch water dispenser consistently produces black algae. This machine becomes a breeding ground for tiny algae particles in short intervals ranging from a month to three months. It's used without being stored, and even after multiple maintenance sessions and cleanings, the service and headquarters insist that the problem is with the water brands, not the device. To prove them wrong, I bought a specific water brand and left it at home for a week with no signs of algae. The issue is clearly with the Bosch dispenser. I'm filing a complaint with the Consumer Arbitration Board because the service provided no solution other than paid maintenance. If it works out in my favor, I'll post it here to help others who are going through the same thing. A reference photo is attached.