For calcium, I have cuttlebone in their cage. I've heard so much controversy about grit that I stopped putting it in the cage for the tiels. I read on so many websites that its dangerous and you should never give it, and on the cockatiel forum I'm on, people said if you're feeding them pellets, seeds, veggies, all the proper nutrition, and cuttlebone, its very unneccessary. Many said its dangerous. All I know is that I don't give them grit anymore because of all the stories I've heard. I give the tiels hard boiled egg with the shell every now and then.