That's interesting about the cuttlebone. I've been doing something similar, and the snails (and sometimes even the shrimp) seem to graze on it readily - cooked salmon vertebrae.
Instead of using tuna for tunafish salad, I'll use some canned salmon. There's always a few vertebrae in each can, and if you get the low/no sodium, packed in water stuff, there's no other ingredients. Because they've been canned (cooked) and packed in liquid for awhile, they're surprisingly soft. I toss a few vertebrae in the tank, and freeze any I have left for later. Any residual meat gets picked off by the fish or shrimp, and over the next day or two, the snails really have at it. It doesn't leave any mess, and it seems like its soft enough for them to rasp on pretty easily.
This is a great list - thank you for posting it! I've noticed individual preferences among my Brigs. If I put some zuchini in, they'll mosey over, but if I put some blanched organic broccoli in... the smaller one will scoot right over!
I'll have to try some of the herbs - that makes perfect sense that many are very high in calcium.
Thanks,
Jane