Hi Guys, noticed my snails are looking a bit tatty, pock marks on shells and white patches, basically they are not getting enough calcium, I assume, The tank is on average a PH of 6.0 - 7.0 perfect for my. Soft water loving tetra and Rasbora but not Snails, I have recently added some Amano shrimp too. My question is can I add something to benefit the snails/shrimp but not alter my water to much, Fish are very content at present. IV heard cuttlefish bone is a good choice. Any advise greatly received.