Hang it in a cage with thick wire for a while to see if he eats. It's usually cuttlefish bones bought in pharmacies.

Do you want this to smell fishy? The following is found online:

"Cuttlebone [also known as cuttlefish bone. You can find it in a Chinese medicine shop. Super cheap. Seafood stalls in the vegetable market can also be found, but it is best to soak the cuttlefish bones in the seafood stalls for a day, then dry them and put them in cages. You don't need to break it, just put it in tiger skin and chew it yourself. When the cuttlefish bone just chews a little and falls out of the cage, it can be broken with pliers and mixed with millet to avoid waste. Many people think it is used to supplement calcium, but I personally think that protein should be supplemented in addition to calcium supplement. ]"