Marc, why do you think several rocks on the topsoil promote mold??? Don't most soils contain the occasional pebble? I don't see how a layer of them on top would cause MOLD... anyway's more to the point... I have proof that it works. You see, when I germinated, I did so in soil, so it was inevitable that some would pop before others. However my smallest one, who has received probably a day or so less light the the others, is also showing the same secondary growth as the others, at the same rate... this leads me to beleive that this did not happen solely of natural maturation. Yes, they are under lights, and growing every moment, so photosynthesis is def. a contributor... but so are the rocks. Why else would the younger plant begin showing secondary growth as well?