I have them too....Fungus gnats.
I live in CincinGnatti.
Mine are in containers, terrariums and a couple Wardian cases.
If you have just a few containers a 1/2 inch of sand will provide a impenetrable barrier that the gnats will not like.
This will disrupt their breeding cycle and help some.
Sweet oil ( walmart 4 bucks) placed in a bottle cap will catch the rouge gnats and keep the flying monkeys down.
Check out this link and google fungus gnats .....pick and choose what is right for you.