If they are Fungus Gnats, put a 1/2" to 1" of sterile sand on top of your soil. (I am assuming a soil grow). Buy some of those yellow sticky Bug cards from a hardware store and put them at Plant level. The Damn larvae live in the soil and the sand will prevent them from getting to the surface. The yellow sticky cards will take care of the flying ones.
Reduce your watering too...the damn things love moist soil.
Kill 'em all. Total eradication, no mercy, protect the Girls at all costs.