After Dimas got over nipping me. (He was actually just in his teen stage and he is still getting over the hormonal changes) I gave him Rainbow Pellets. And yes, I know these arent the healthiest, but it got him into eating them. After I knew he was eating the Rainbow, I got him natural non-colored pellets. He didnt want them at first but I kept handfeeding it to him. With him dropping it like a noodle

. After he ate one he started eating the ones im his bowl. And as for the cockatiels they are eating the same pellets. My trick is not getting the bird the package that says is for its size, but one size smaller. Like this:
Finch & Parakeet: Finch and Parakeet size ( They dont have a size any smaller for them sothey get their normal sized food )
Cockatiels, Lovebirds, etc.: Finch and Parakeet sized
Conures, and birds their size: Cockatiel or Lovebird sized food
Macaws, and Large birds: Conure sized food
But this only applies to Kaytees Pellets. And as soon as I can Im going to get my parrots Harrisons.
