Thank you John, I was just going to google the same. I was not doubting what you were saying, I just couldn't see how it could be measurably possible in a time frame that makes sense to my obviously non-scientific mind. I want to know why I should use something before I attempt it as well. But in defense of my way of thinking, I will point out where it states 'one application can last 10 years', 'very slow release', and 'slow release over a long period of time'. I am trying it for the first time, due to reading previous posts where it is stated that the granite grit is being used as a seed starter medium. I have a nightmarish fungus gnat infestation happening right now and I was hoping that using the granite grit straight would help to eliminate the gnats. I thought I had done my research and upon reading your post it got me thinking enough to question. Should have googled first! Linda Okotoks, AB Canada