I have been for a year and a half now, and still on the same bottle with four tanks. It is pure potassium nitrate & works very well, no complaints here.Phillyman said:If you want to get KNO3 right away you can use Greenlight stump remover which I found at Lowes. It is reported to be pure KNO3.I have been using it with no problems. Any one else using this?