These flies are amazingly fast and incredibly tiny. They only appear when I disturb my plants, spinning around and then disappearing again. Is this a problem?
Ancient Mariner - I have those too. ES is probably correct - fungus gnats. They are more prevalent during Winter in my area.
I keep them under cotrol by using Mosquito Bits Tea (4T Bits per gallon of very warm water. Shake well and let it steep a few hours.)
During Winter, orchids in the back corner of my grow room are particularly susceptible. Once a month those orchids are watered with the tea and voila, no more gnats. ROBB