I am having some issues with my tank. Brownish red stuff is showing up on sand. Greyish stuff showing up on live rock. The greyish stuf can be mostly blown off by a baster but some will stay. Nitrate 0 (just tested). Phosphates at 0.025ppm. Flow is 3x Tunze 6025, and return pump magdrive 9.5 going to a squid. Any ideas as to what the redish brown and greyish stuff is? What is causing it? How to get rid of it?
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http://i75.photobucket.com/albums/i305/arb...ey/DSCN1340.jpg
http://i75.photobucket.com/albums/i305/arb...ey/DSCN1341.jpg