Hi Linda, I did the 'quickly Googling' because I'd come off the tennis court at 11:10 pm and was ready for a shower and bed! It is kind of hard to envisage how something as apparently hard and inert as granite can release sufficient material to be useful, but it does. We are talking concentrations in the low ppm, and below in some cases. I have never considered using the grit as a starter medium but there's no reason why it might not work. I would certainly experiment - your own experience beats the heck out of reading about the 'right' or 'only' way to do things in books. I've never grown anything under lights, which I where I assume you have the fungus gnat problem? They generally prefer warm damp organic conditions. A 1/2" layer of granite grit on your seed pots/trays and letting them dry out somewhat between waterings might be a good place to start? You can whack them with an insecticide to get the levels down quickly whist you adjust your conditions. Best, J. John T Lonsdale PhD 407 Edgewood Drive, Exton, Pennsylvania 19341, USA Home: 610 594 9232 Cell: 484 678 9856 Fax: 801 327 1266 Visit "Edgewood" - The Lonsdale Garden at http://www.edgewoodgardens.net/ USDA Zone 6b