Last year, we had a really bad problem with mustard algae, so this year we've been extra dilligent testing the water and keeping the chlorine level a little on the high side. The pool is crystal clear and has been all season long, however, I keep finding smudges of something that appears anywhere from yellowish/green to yellowish/orange on the bottom. It doesn't seem to react like algae if I run the brush or the edge of the skimmer over it because it doesn't poof into a little cloud and disappear. I have to use the vacuum to remove it, sometimes needing to scrub over it several times. In general, I don't see it at all until the filter is turned on. The circulating of the water seems to make it appear.
I don't see much change in FC levels overnight, it stays pretty consistent and I haven't let it drop below 3 since we opened the pool. I do need to lower the ph and TA levels, though I don't think that would cause the smudges to appear.
Here are my numbers this morning. I have a good test kit, so I think the numbers are accurate:
TC - 5
FC - 3
ph - 8.4
TA - 180
CYA - 30
Water temp is currently 76 degrees.
We live in an old neighborhood with lots of huge, mature trees around. A few branches of a large maple tree hang over the pool. Could this be dirt or pollen? Would pollen require scrubbing to remove? I've become obsessed with this, I don't want to deal with another algae outbreak.
Also, disregard the filter listed in my signature. I haven't updated my sig. yet, but we are now running a sand filter (not sure of the hp, I'll have to go take a look at it).