How can I treat the mold on the top of my indoor plant soil?

1. Scoop away the mold. If you see mold on your soil, it is likely confined to the top layer. ...
2. Let the soil dry. Once the mold is scooped out, or your plant has been repotted, allow the soil to dry out before watering it again. ...
3. Add a natural anti-fungal to your soil. ...
4. Keep the soil clean.

mold growing over the surface of houseplant potting soil is usually a harmless saprophytic fungus. ... Overwatering the plant, poor drainage, and old or contaminated potting soil encourage saprophytic fungus, which feeds on the decaying organic matter in soggy soil

It may likely be excessive moisture. I have a self watering outdoor patio planter with brown mold under the weed barrier cover.

Mix hydrogen peroxide with water in a spray bottle and spray several times a week. About one part hydrogen peroxide to ten parts water. It will eventually kill the mold. Just try to not get much on the plant leaves .

Thank you!