Why does it do this?

[Robert59]

ot looks like sand worms all rolled up my tank is like a all tiny particles I the water and can't get crystal clear what am I doing wrong help r2r thanks

 

[saltyfilmfolks]

Is the sand Being blown around ? Can't really tell.

 

[reeferfoxx]

Kind of looks like the diatoms are making the surface harden and the current is trying to move it around?

 

[Animagus]

It's kind of hard to tell from those pictures, but there are certain worms that construct their tubes out of sand grains. (Figure 10. below)

http://reefkeeping.com/issues/2003-05/rs/