Hi group an observation from my tank is that my mystery snails have a degeneration of there shells and by my reckoning it must be Calcium lacking in the water. I may be wrong but any clues would help. Also if it is calcium how can I safely add some so as not to hurt my fish? My water is pH 7.2 KH 4 Gh 7 cheers Neil From the" Land Down Under" icq 13931687