Beginner question about sand changes

[Seadoc]

Hi all,

I am currently at month 2 with tank cycled. CUC is doing its job pulling what I think are diatoms from sand, rock and glass. My question is: what are the dark dots underneath the sand surface? Should
I clean them with the next water change? Sooner?

Thanks in advance.

 

[brandon429]

Those look look like gas pockets from photosynthesizing algae or perhaps waste gasses from bacteria that respire co2. common for new bed aging and the lighting makes them look dark

 

[Seadoc]

Awesome. Thanks!!!

 

[Sparkymarc]

+1. Gas pockets. You could stir the sand a little and see if bubbles come up

 

[RocketEngineer]

They are likely oxygen bubbles from algae that is getting light through the glass. Nothing to worry about.