Ive had my 75 gallon tank for about 5 month. It is perfectly cycled. Params r 0/0/5-10. I have 4 angels, 4 platys and 8 tetras. Since ive had the tank cycled ( about 4 months) ive been through 6 mystery snails. I know snails are more prone to nitrites and nitrates but ive been very adamant with my water params and pwc. I do have very soft water, but i cannot see how that would kill snails within 3-4 weeks if im adding calcium. I loved my snails and will not buy more if my soft water makes them suffer. My husband thinks the fish pick on them and given angel's behavior it would not surprise me, but i personally never seen any fish even notice the snails. Am I doomed for mystery snails? Oh btw, i raise ramhorns for my puffers amd they thrive in the same soft water. I have a few egg laying adults that have lived for months.