Black algae on sand

[MatheusOlib]

Hello, I’m from Brasil so sorry for any error

I’m in trouble with my sand bad, some algae is getting control over it. Looks like a hair algae, a black one, and sticks several grains of sand.

 

[blaxsun]

Is it black or dark green?

 

[MatheusOlib]

Is it black or dark green?

Dark green, very dark