Drench the pot soil with Hydrogen Peroxide <1% (mix 4 part water with Hydrogen Peroxide 3%).
So tiny gnats will try to jump around to escape. You can spray them with Hydrogen Peroxide or Home-made Neem Oil Pesticides.
The downsides of using Hydrogen Peroxide is killing all the microbes in the soil (both good and bad).
Hydrogen Peroxide helps with root rot (caused by fungi and bacteria in the soil, also caused by excessive moisture in the soil due to overwatering), by killing fungi and bacteria in the soil and restore oxygen. The extra oxygen also help the roots to absorb more nutrient.
I add mulch on top of the soil to discourage gnats to continue to lay eggs.
