My starter doubles or more in size, and seems to work pretty well, but I think it should be doing better. I see some people get starters that look very strong with large bubbles and they make great bread. My bubbles are always smaller but plentiful, but I am still not sure it is the best it can be. I use 70 grams of rye flour, 140 grams of high protein bread flour and 140 grams of high protein fine ground whole wheat flour in my starter mix. Does anyone have suggestions as to whether this is a good mix or not?