If they are brownish-black they're most likely fungus gnats. These need a wet enviroment to live and their tiny maggots can be seen crawling around the soil surface. If you have this it's an easy fix...quit watering so much. A thin layer of sandy soil over the surface will help too, as long as the surface is not kept constantly wet. Gnats need a wet environment to survive so if they're not coming from the pot pots then there must be another source nearby.