To me, amprollium is counterproductive and does nothing for the bird in the long run, which is why so many report getting coccidiosis in their flocks after they stop feeding the medicated feeds and switch to an all flock feed. It's a thiamine blocker and thiamine is important to a growing bird, so I never use the medicated feeds or any other med, for that matter. It's individual preference, though, so no one is going to tell you not to use it.
Feeding FF is one way to help prevent coccidiosis already, so feeding medicated FF is sort of redundant but in a less efficient way. You can do it but it won't do much either way for the bird and won't do as much as feeding the probiotics in the FF.
You can also give the birds early exposure~day one~to the levels of coccidia in your local soils by placing a clump of sod in their brooder for them to partake of. I take that one step further and brood my chicks right on the same deep litter my flock has been living on for over a year so they will get a good exposure to the levels in the coop as well.
The first two weeks of their lives is when they are best able to form antibodies for environmental pathogens and is why broody raised chicks are so much more healthy than those brooded in the house and then placed out with the big flock after they are 4 wks of age or more...that's about the age we get the most reports of coccidiosis in young birds.
