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Good post all around Steve and I know you are not taking my post the wrong way. I have found obviously, depending on the severity of the moss and lichen there will always be granule loss caused by these " parasites ". It is in deed feeding on the lime stone but as far as " eating and digesting " the granules I really don't know. There is no doubt that the moss and Lichen are " dislodging the granules but how? They take such a hold onto the shingle is it the granules that they " latch onto " to " suck " out the limestone causing the granules to lose there hold? I don't know but this what I do know. I have cleaned roofs where you would have sworn someone power washed it previously, but that was not the case and I know that because of the number of times it has happened and the HO are pretty honest about it. So as I continued to learn I found that the moss and Lichen can " fall off " to the gutter or ground. On inspection I was amazed to see that the lichen is not a thin flat growth but actually an amazing " fat,thick" growth which is very deceiving to the HO from the ground. Of course on the bottom I find graules embeded in the Lichen. Why do they fall off? Does it die and fall off? I don't think so, because when I find the moss or lichen which had dislodged it seems to still be " alive " fresh so to say. So what happened? Did it have a " hold " on the granules " sucked out the limestone causing the granules to give way, causing it to lose its grip? On homes that I have returned to where the lichen and moss have been so heavy I find the following. It is obviously dead it is also hard,brittle and thick. I can easily remove it pretty much as a whole piece some granules are embeded but I am impressed in the overall condition of the shingle and minimal granule loss. I rinsed about one hundred and fifty or two hundred homes before I stopped so I am basing my findings on my experiance in " blasting " off lichen and moss. When I rinsed the lichen and moss it had no choice but to give way, same as if I used a power washer. Being forced off, the graules will go with it. Killing the lichen and moss, letting it decay and roll off definitely is leaving behind more granules. Now take into consideration no one will really notice granule loss from the ground no matter what you did unless it was really infested to where it maybe should have been replaced. "My layperson explanation to our customers is that Gleocapsa Magma is living off the limestone filler, while the other infestation is living on the mineral content, ie, the shingles's color granules-- thus the bare spots left behind when it is eradicated". There are many meanings for the word eradicated, one is to " tear up by the roots, to get rid of by the roots" " to tear out of the ground" is that what we are doing to the moss and Lichen? I don't think that is the definition you meant. The shingles and the granules have " color" to them, I have found that just heavy Gleocapsa Magma can remove the color from the granules giving the appearance of granules loss although the granules are indeed still there just color less.