Pointy-top snails cannot crawl on sand and fall over and die of starvation. Get ceriths and chestnut turbos. Also, provide your hermit shells of the same species they're weaRing, but just a little larger---the crabs themselves will suffer if they can't get new shells in a larger size. Ultimately they do reach species max, but until then, they need a succession of shells. It's life or death for the crabs, too.