Hello - I have a rectangular pool with a sitting ledge that goes all along the width of pool in the shallow end. The last few weeks I've noticed there is a faint red mark that goes along the length of the face of this sitting ledge. My FC hovered between 4 and 5 in August and has been at least a 6 from September on. I did an OCLT with no chlorine loss.
My numbers today are:
When I brush along the bottom of the pool the brush does hit the face of this sitting ledge so I'm wondering if this is the brush leaving a mark or if it is an algae. It is in the shallow end near the pool bottom so the circulation is probably not the best. Any ideas on my next steps to figuring it out? Thanks!
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Also - I checked the pool brush and it is clean. The only thing that is hitting the sitting ledge is the black plastic or the bristles themselves.