How does sand change in to sand stone?

why to change it in the first place. in the first place why we should chnge the sand in the filter, why can't we jus try to wash it where as it is still in place ,how ever if it is still needed to...

Sand. Sand is a form a eroded igneous rocks, which is then undergoes cementation/compact to form sandstone.

Sandstone is a reddie blue stone that has yellow spots on

One way would be that the water never really gets crystal clear. A good rule of thumb is change sand every 5 years. Of course use the correct grade of sand and use the filter manufacturers...

No.