Excellent question and one I'm dealing with right now. I have one of those long, low feeders for the chick start, and a taller bowl for the moms, but I'm sure everybody's eating everybody's food. I'm not as concerned I guess because I feed organic lay crumbles to the grown-ups (no antibiotics or growth hormones or whatever). I do, however, feed the medicated "flock raiser" to the chicks after talking with the feed store guy. He said he did an experiment: 25 chicks on organic starter...25 on medicated. He said he lost several chicks on the organic, none on the medicated. He claimed both situations were the same, but I know the guy, and he's not a scientist. In any event, I don't worm or medicate anybody and I am dealing with leg mites, so I figured the medicated was the way to go for the babies, the organic crumbles won't hurt them, and the moms couldn't be OVERmedicated, because they don't get any other meds. Make sense?
And please, if anyone sees a problem with this, feel free....
P.S. Big birds seem to like the bigger food - little ones go for the littler stuff while they're tiny.
Medicated feed is only for cocci, nothing else. It won't help with mites or worms, it does not contain antibiotics it should contain amporilium (sp?) there is another one out there but this is the one you want, Purina make one with it.
On the chick starter, I saw on another post where the person made a feeder cover out of an upside down white bucket (one of the 5 gallon types) with holes cut in it to cover the feed that only the chick would be able to fit, another used a plastic crate that they could get in and the other big girls couldn't.
On the babies eating layer feed, make sure you put the feeder up high enough that they can't reach it. Shoulder height for the adults will hopefully be high enough for a while.
1000, even 100 years ago, people didn't have specially made feed like starter, grower, layer, broiler, medicated, etc. ALL chickens would have gotten the same thing, some kind of a mixture of grain and corn (what we feed as scratch nowadays). So I wouldn't worry about the chicks eating the organic layer feed, but I would be concerned with the hens eating medicated feed. I wouldn't want to know what got into those eggs!
Try switching the chicks onto non-medicated. As long as they're in the coop, in dry, clean bedding, it is unlikely one would develop Coccidiosis.
Actually, a while back I was in the feed store and I saw a chick feed with Tetracycline, the well known antibiotic and medicine we know mainly as a potent antibacterial and acne cleanser. This was their main line of chick feed, and when I first started with my chicks (now getting ready to lay eggs!) I made sure my feed just had amprolium, which is non-antibiotic Coccidiostat. Non-medicated feed was unavailable!
I turned a square bucket (cat litter box) on its side and a brick on top and faced it toward a wall where only the chicks could get inside and put their feed inside it. The big girls couldn't go inside to eat their food and the chicks were not interested in pellets.
Yes, I forgot to mention that - very important. That's why oyster shells, as well, should not be provided to young chicks. It causes over development in the bones, I believe, and can poison them as well. I like K8tieCat's Idea - perhaps something like a large Rubbermaid storage container with a hole in it would work as well - harder for the big hens to flip over. Maybe create a barrier around the hens' feeder as well so that the chicks can't climb over (it wouldn't work for very long, though). As others said, I think hanging it is the best solution for now.