I have also battled the gnat problem with fox farms soil, but a few simple ways to combat this is to put a 1inch layer of of perlite on top of your soil. the gnats dont seem to bother the plant much, but they are much more interested in the soil, so laying perlite down makes it almost impossible for them to reach the soil. I've also used yellow sticky traps and made a home made concoction of apple cider vinegar, a few tablespoons of sugar, and a few drops of dish soap. put that in a jar. The gnats will fly in there, but they get caught in the soap and end up dying. hope this helps. ill post some pics of my setup in a few