ID Please

[RMS18]

Normally when the pumps are on the sand has a brownish dusting, no hair or bubbles. When I turn off the pumps to do a water change, the brown film starts to form a slime like texture and floats into the water column as in pictures. Only on sand no Rock or corals.

Running a BRS 7 sage Rodi system.

Thanks!

 

[Oscaror]

Looks like diatoms

 

[RMS18]

Looks like diatoms

That's a relief... Not sure how they are getting in tho. TDS reads 0 on meter after Rodi.