I also use salt, and raise the temp to treat ich, my anistrus had no problem tolerating a salinity of 3ppt and above(ppt=parts per thousand (sea water is approx 35ppt).
3 ppt is the magic concentration for killing ich, at that concentration any of the ich larvae that either hatch from the fish, or out of the gravel will be killed. When it is on the fish, or dorment in the substrate, ich is immune to any salt or medication. This is why the treatment must be allowed to work over a matter of weeks.