Sand Quality degrading.

[AquaLord]

I am new to Aquariums as a whole and and am currently experimenting with Freshwater tank.




https://imgur.com/a/ZbvbOXR
The above attached photos (3) show the coloration of the sand in my Fresh water tank.
The deposits are not even on the sand since I disturbed them to mix the sand.



Can anyone at a glance tell me reason for such deep discoloration and how I can avoid it?

 

[King Fisher]

Detritus looks to be the culprit. Also, diatoms will create this as well especially close to the glass. Diatoms usually will spread across the surface of the sand and really looks bad on white.