water to bring it down to the correct salinity. And banker, when alkalinity rises to quickly or to high it causes the calcium to solidify into calcium carbonate I believe its called. This can happen easily if salt is dumped in large amounts and yes it will lower calcium levels in that water since it has precipitated. It doesn't ruin the water really just leaves you with a bunch of sediment and lower reef levels. This is also known to happen when dosing alkalinity. Same thing, if to fast or to high it will happen to the calcium in your tank and there isn't anything you can do but watch it run its course and it can be harmful to corals since its a very fine sediment.