You can feed your sourdough with all cereal flours. To preserve the characteristics of our sourdough starter, wholemeal rye flour is best suited. But starters made from wheat, spelt and extraction flours are also possible. Basically, it is advisable to feed your sourdough with the type of flour you also want to bake with. Then the microbes are already ideally set for the fermentation of the dough.
Should your starter weaken a little, it is best to feed it again with wholemeal rye flour. Rye itself is the most reliable source of the necessary microflora and can thus "animate" your starter with good microbes. Wholemeal flour also contains more trace elements than extracted flour, which can also lead to a more stable and less susceptible starter.