My snails turn there noses

to the calcium blocks, from the recipe that was a stickies from MsJ. My fish seem to try to eat them, is that bad for the fish? can they get kidney stones? Anyone have any suggestions on getting my snails calcium, they need it. And Snello is usually eaten by my other fish too before the snails have a chance, even without the fish food recipe. If i put it in at night, my Cori's eat it! =/

ph is kinda high like 7.8 but its lower in the tank like 7.2 i think that's from the driftwood. Hardiness is like 150. There shells are looking cracked and unhealthy. but they do eat shrimp pellets. Ive put zucchini in before and they didn't seem to like it. =/