Are they fungus gnats? Don't put anything on until you're certain of what they are.
Make sure you're letting the top of the soil dry out before you water, otherwise you're encouraging fungus gnats (if that's what they are) to complete their lifecycles. They lay eggs in the soil; the larvae eat plant roots. Not a massive problem, and I have them in my grow room (their numbers are up and down - thought they went extinct but a new wave appeared this morning).