weird crunchy layer on sand?

[rookiegirl]

I was moving my sand around a bit as i noticed a bit of algae building up in one corner and realized there was a layer of flaky, crunchy pieces in the sand. The top layer had formed some clumps like cereal flakes that appears to just be sand clumped together.

Any ideas what may have caused this?

[snorvich]

What kind of sand? What is your pH?

[rookiegirl]

Ph is at 8.1 and i used caribsea aragamax i think for sand...2 bags dry 2 bags live.