Is your water low in GH & KH? If so, cuttlebone can be helpful in producing a normal, strong shell. It can be clipped with a suction cup, and more easily simlpy rubberbanded to a rock (it will float otherwise). The soft side of the cuttlebone should be the exposed side - use your fingernail to test - one side is hard, the other soft and chalky.
If your water is at least moderately hard (say GH & KH 7-9 or more), you may not need to supplement minerals if your do regular water changes to maintain GH/KH levels. Snails can extract these from the water if sufficient is present.
Cuttlebone can stay in the water indefinitely, but the soft part may eventually be eaten away or may simply dissolve eventually.
HTH