It's algae. Mold will be black or white with a funky smell. It will stop when the canopy gets big enough to block light from the soil or you could use algicide. Not sure how that would work in soil though.
Algae will rob a very small amount of nutrients, not enough to concern yourself about. Cultivate the top inch of your pots soil if you are worried about it but like others have said, once the canopy shade the base the algea will die off.
Algae will rob a very small amount of nutrients, not enough to concern yourself about. Cultivate the top inch of your pots soil if you are worried about it but like others have said, once the canopy shade the base the algea will die off.
You can cover the top of the pots with black plastic (like from a trash bag) with little holes to allow some aeration of the soil,
while still depriving the algae of light.