Have you seen [this](http://gardening.stackexchange.com/questions/20611/indoor-gardening-with-rockwool) post? Makes me cringe to think that this individual with at least *two* black thumbs and not even a *basic* understanding of how plants or gardening work now considers hydroponics. And just to use the leftovers from some insulating job. <sigh>
Any idea how to answer this without stepping on some rather sensitive toes? (I don't.)