Need some help with sand

[mouse03245]

Hi guys. i need some help to indentify what is in my sand! All my test are on track. ph 8.3 ammon. 0 nitrite 0 nitrate 5ppm (kinda on track) alk is normal water temp is 80 deg. specofic gravity 1.024. it is a 55 gal. reef with lr and a cleanup crew, mushrooms and a few polyps. we have been having problems with diatoms and a while back we had a problem with cyno (forgot the rest of the name) the diatoms r still there but not the cyno. Any help would be apreciated.We suck it out and then a few days later its back. :help:

 

[mouse03245]

Here is a bigger picture,if it helps any.

 

[beth]

Does that kinda stick together or does it easily turn over?
How is your water movement at the bottom of the tank?
What detritivores do you have for your sandbed?