Abstract: The invention pertains to coral sand, more particularly to a composition of coral algae, shell sand and ascorbate being useful as an additive for the improvement of the quality, including the taste, of drinking water, that is as a water improvement agent. The composition is as follows: 5 to 90% coral algae, 5 to 90% shell sand, 0.1 to 8% ascorbic acid salt, and it is chosen so that by the addition of 0.5 g to 1 liter of water is the mixture is emerging with a pH from 7 to 8.5. If the product in addition contains a suitable gelling agent, this entails that any bacteria formerly present, after addition of the water improvement agent according to the invention, no longer exist in the free solution.