Fungus gnats are the most common insect pest when it comes to microgreens. Bottom watering and reducing the number of times you water is the best way to prevent fungus gnats. Only water when the soil is dry.

If you do have fungus gnats, here is a link to a forum where one of the Free Microgreen Growing Course members asked how to get rid of them. My answer is in the reply. Here is a link to that forum.