Fungus gnats are actually small houseflies. They are dark in color and measure about a sixteenth of an inch long. These gnats can become a problem for homeowners who keep potted plants indoors. Often the gnats are a result of over-watering a plant, or filling its pot with organic type soils. Fungus gnats won't hurt your plants, but they are a nuisance. There are ways to get rid of these pesky fungus gnats.
Water you plants less. The roots of the plants begin to root when there is too much water, and the gnats feast on dying roots. Allow your roots to dry out a bit and become healthy again. Fungus gnats don't eat healthy roots.
Change out the soil in your pot. Peat moss and other organic soils provide fungus gnats with the best place to lay eggs and increase the fungus gnat population. Instead, use a pasteurized container mix from your local garden center.
Place a one inch layer of sand on top of your pasteurized container mix. Fungus gnat larvae will not travel deeper than that, and they cannot survive in the sand.
Trap the fungus gnats by applying yellow sticky pads inside of your plant's pot. You can get these sticky pads at your local garden center, or online.