Good plenty of postings on this Forum and other care sheets that report on the benefits of providing cuttlefish bone in your tort's habitat for them to get their calcium allowances.
Every time I read post about cuttlefish, I always hope a little inside it is about owning living cuttlefish, and not their bones. But cuttlefish bone are a great source of calcium, the trouble is getting your torts to eat it.
I have a fresh cuttle bone available all the time. In their outdoor pen I put a stake in the ground and screw the cuttle bone to it so they can bite at it without it scooting away from them or being in the dirt. Works well.