I use only oyster shell grit because it provides the calcium
benefits and not the indigestable gravel (rock). It was
believed several decades ago that parrots needed gravel or
grit for digestion like chickens and turkeys. Provide good
sources of calcium in cuttlefish bone, powdered
oystershell,mineral blocks, and broccoli, okra, and other
greens have calcium. Parrot babies need free access to it
for good growth and Parrot hens during breeding season.