I actually had excellent success using diatomaceous earth on gnats. If you havent heard of it before, google it. It's like razorblade rock dust. Bugs that come into contact with it literally get cut open and die. I spread a handful of the stuff over the soil on top of the pot, I stick some in the drainage holes, too. Do this after watering to prevent watering the dust into your soil. This creates a barrier where nothing wants to land on the dust, or crawl out of it. The stuff is made from silica, so there may be some benefit to the plant as well from using this stuff (silica helps beef up cell walls?). You can vacuum off the layer of dust before watering, also. Just make sure you put some back down for insurance.
Keep your room clean and get some sticky traps if you want to see the visible difference your making battling bugs... and watch the little buggers disappear. Neat stuff, just use a mask.
