For drinking water: maybe one crystal per tumbler of water. It should make the water "just pink".

For antiseptic, enough should be added to make a bright pink colour.

For antifungal, a deep red colour, like red wine.

For you pyro's out there, mix 1:1 with table sugar on a flat hard surface and crush/mash with the back of a metal spoon. See the pretty lights and smoke!