Melitta 178582 Entkalker Kaffeevollautomaten Anti Calc espresso powder 2 bags per 40g (household goods)
As can be seen even in the product description of kalkreinigers, is the descaler to "100% citric acid" common citric acid. 5kg Pure citric acid, in crystalline form, of Purux, you get in a Marketplace dealer for about 23.85 incl. Shipping. Even