Hello Iam from germany too .
Ich use T.A nutrients the flora series. My tap water is very soft ec 0.2 and I use the micro component for soft water .
You need the micro for soft water .
Also three components for veg and bloom in different formulation . The flora grow
Flora micro for Hardcore water and the bloom . It is a high quality fertilizer and very ph stable in the Reservoir .
Use no air stones keep the solution fresh only a waterpump