Answer: These sound like fungus gnats. These breed in overly wet soil. The first thing to do is cut back on watering the plants. Most plants like soil that is evenly moist like a wrung out sponge, not sopping wet all the time. Allow the soil surface to dry out between waterings. The dry soil surface prevents the gnats from breeding. This should stop the gnats in a week or two.
You can stop them immediately by using a soil drench containing Bt (Bacillis thurengiensis) and labeled for fungus gnats such as Gnatrol.
Or, if you have plants such as papyrus that prefer a constantly wet soil, cover the soil surface with a fast draining, fast drying layer of coarse sand or fine gravel. The gnats will disappear in a week or two as the existing adults die off.
I hope this helps!
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