I have been fighting this stuff for the past 2 seasons. I am not sure if it is mustard algae or if it is just pool dust/debris that my sand filter cannot catch. I have tried vacuuming it to waste, but it seems to just come back. Can someone please help me identify what this stuff is and what I should be doing to remove it. My pool water is pretty clear (as seen in the 3rd photo) except that this stuff is very visible on the bottom of the pool. Also, this stuff is only on the bottom of the pool, it does not appear on the side walls. Thanks!!
Test results as of 5/3/11:
Water pH: 7.5