With Kiwi, I notice that he seems to just rip up cuttlebones for fun (I'm sure he ingests some, but he mostly uses them as a toy) while he actually eats on the Manu block in his cage. However, I've actually researched the Manu, and the reason South American parrots eat it isn't it's nutritional content per se. They eat it in nature because it's a form of natural clay that counteracts the effects of toxic seeds they eat (especially in the dry season) as well as serving as a kind of "grit" to help them digest food. From what I've found, mineral content is basically an added bonus of the stuff. It may be worth a try, your bird may instinctually recognize the "taste" as something he would eat in nature.
