That's what I thought too, it farm the phosphorus in the medium, I typically don't use it unless I'm my organic soil, but have heard people benefit some from it using synthetics as well. Typically I use less, mostly just use in act add molasses and oatmeal flour, after 24-36hours (no more than 36) they reproduce. There's a video on kis about it, in theory the mammoth microbes should reproduce some as well. I only use it a few times in a grow because of that. So far so good though, won't use again until I start flower, and probably a third mid flower, going to make this free sample last lol