I know they surprised me the first time I saw them. But then, I couldn't STOP seeing the pesky things. Gnats often "sprout" out of seemingly nowhere, but in reality, they likely hitched a ride into your house by way of the soil in your pots.
Now, they don't seem to stray far from my houseplants, and they don't really harm the plants. (Perhaps they even help feed the spiders in my house!) But if you'd like to get rid of them without chemicals, here are a few easy DIY ways to get rid of them.
Buy a carnivorous plant! YAY! More plants! You're welcome.
Cut out a piece of cardboard, preferably a light color, in the shape of a plant tag. Slather it with a thin layer of honey, and stick it in your potted plant.
Reuse a little glass jar- fill it with a few tablespoons of apple cider vinegar and add a few drops of soap. Swirl it around and place it near your plant. The soap helps coat the gnat and traps it, while the vinegar attracts them. I recommend doing this for a few days, changing it out every day or so.
Use the same trick above, except using a small plastic bottle. Cut the top off, invert it, and fill with a vinegar/sugar solution (1/4 cup vinegar and about 3 tablespoons of sugar). The gnats go down and can't come back up.