Actually, the larvae of those things can do damage to the roots of your plants. There is an easy way to control them, however: Mosquito Dunks. The same Bt israelensis that kills mosquito larvae works on fungus gnat larvae, as well. Just break off a small piece of one, and drop it in - one dunk will provide enough for 8-10 EBs (they say that one works for a pond that is 10 sq ft, for 30 days). I use them in the EBs, plus indoors in hydroponics, in the off season, and never have a problem with fungus gnats.
