I give my birds red grit, which has crushed granite, oyster shell, and charcoal, and coated in a pink mineral powder.
Oyster shell and charcoal are very important, but you may want to add some granite, since it's the main part of the grit that aids in digestion (since it's so hard and not easily broken down like oyster shell). Usually chicken grit is closer to the size they need. But anything parakeet sized is too small usually. Even chick grit will do, but once you start getting into the small cage bird size...the pigeons look at it with this confused look, haha.