Something blue/green on soil

Hi guys/gals,

2 of my pots have a very dark blue/green layer on top, it's hard to see in this photo but it's the best angle I could get to try and show it... I included another photo to show how the normal pots look.
Is this some sort of mold or something? I usually have a fan on them but haven't the last few days. The grow tent is open all day/night as they are still in veg and no smell yet.

Would it be enough if I were to just scrape away a couple inches off the top and replace with fresh soil?

Soil is sunshine mix #4 with gaia green added but the top couple inches are a potting mix because I ran out of sunshine mix at the time. I would be replacing the couple inches with #4 though.

Thank you for any advise!

I can't see it in your pictures, but it sounds like algae. It's an invasive plant that will grow on moist surfaces.

Yes, you can scrape it off without problem.

rollitup said:

I can't see it in your pictures, but it sounds like algae. It's an invasive plant that will grow on moist surfaces.

Yes, you can scrape it off without problem.

Click to expand...

Thank you!