Whats that brown layer all across the top layer of my sandbed?

[Weehawken64]

What is this and what does it mean. Thanks

 

[Rutrag]

It sounds like diatoms. Most new tanks go through a phase of it. After they consume all the silicate in the water, they tend to fade back all on their own.

 

[Weehawken64]

Ok cool. Thanks rutrag