Once your starter is established and doubling within a few hours of each feeding, you can transition it to a different flour. Sourdough starters can be finicky, so make the transition slowly for the best results. To transition flours, feed half the amount of the original flour (I recommend bread flour) and half the amount of the target flour. Continue decreasing the original flour and increasing the target flour over the course of the next three feedings until you're only using the target flour.