Depending on the size of rock I usually either put it in a tub and cycle the water daily (or more) or for small pieces I put them in the toilet tank that way they get fresh water every flush (with 5 kids that is quite often). But it you see salt (not where the salt use to be) then you have a ways to go, but it in a tub and heat the water to 90 degrees, it will speed up the salt dissolving process.