I have a 35,000 gallon inground SWG vinyl liner pool. Pool chemistry is in line. This afternoon the FC was 7.8 and the CC was zero. PH was 7.4. I use a Taylor 2006 test kit. This evening I noticed black in the crevice around my steps. I used a brush and it peeled out rubbery black strips. It was mainly in this area with a tiny amount around the skimmer. My chlorine levels are holding just fine. I’m not noticing any drop off. Could this possibly be black algae? If not, does anyone have any ideas what it could be?
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