Green in my sandbed?

[zsqure]

My sand bed has what looks like green alge "leaching" into it. The green can be seen when looked at the sand bed along the edge of the glass. I guess I need to post a pic.

 

[hot883]

It's just algea on the glass.

 

[salty cheese]

Below the sandbed and on the front of the glass, right?
If so, that sounds like a type of cyanobacteria, harmless IMO.