Starters can be made using any mix of flour you prefer. Bakers around the world use all sorts of different flour mixes: Rye, whole wheat, and all-purpose flour are common. I prefer a mix of 90% bread flour (for strength) and 10% rye (for nutrient content and enzymatic activity). Different flour mixes will cause changes in aroma, dough consistency, speed of fermentation, and height of peak. Higher percentages of whole grain in a starter can supply more nutrients and enzymatic activity which can make the starter more active while also giving the starter a more sour flavor. Higher percentages of white flour in a starter can make the starter more sweet in aroma and flavor. While changing the flour will change the physiology and behavior of the starter, it’s part of what will make your starter unique!I like to prepare a bowl of my flour mix ahead of time. This way, I’m not measuring out the individual flours at every feed. In my Flour Feed Bowl, I whisk together 450g bread flour and 50g rye flour. This 500g flour mix usually lasts me a week or two if I’m feeding daily.