I started my 8 chicks on a 5 pound bag of organic chick starter "crumbles" and when in less than two weeks it looked like I was running out I found a local (well, 25 miles away) feed store that carried organic chicken feed and purchased a 10 lb tub or their organic chick feed and a 50 lb bag of organic chick "grower" feed. The guy at the feed store told me that when the 10lb tub of starter ran out, just switch them to the grower feed. About three weeks into the 10lb tub (5 weeks of age total) I was down to about a 1/4 of a tub and I dumped in maybe two pounds of the grower and mixed it in with the starter. A week later they are taking all grower feed. I don't know if this is ideal or the way a long-term expert would do it but my chicks are thriving and haven't had any adverse reaction to the change in their diets.