Product review (5 stars): This handles the white dust issue!!!
I did a lot of searching for a product that would help curtail the white dust that is created by a humidifier. This does what it says it will, am very happy with the results.  Our water is medium hard and this works great.  We run the ultra sonic humidifier every night so is important to have this product which is made for the ultra sonic machines. Only a cap full per tank.  I ordered 3 bottles of this, it was shipped VERY fast!  I will reorder when I need more.