OCLT passed, pool clear, but little patches of green

Prav

0
LifeTime Supporter
Nov 23, 2010
95
Miami, FL
Yesterday, my eyes were drawn to some extremely small (<1/16th inch) patches of (dark) green at the tile-line in a couple of corners of the pool. They felt algae-ish (read: slimy) and when I rubbed a puck on them, they seemed to fade. Unfortunately, didn't take pics.

FC: 6 on Saturday evening; 6 Sunday morning; 5 Sunday evening after full day of sun (added some more, did not test again)
CC: 0
pH: 7.6
CYA: 50
CH: 380
ALK: 80
Borates: 50
Temp: 87
Water: Clear (can clearly see main-drain screws)
Other observations: lots of little debris (bugs, pollen, dirt) in water, but nothing that a little filtration won't take care of.

OCLT passed (yes, I did remove the puck floater) both last weekend and yesterday.

So, a few questions:

(a) In theory, should I have raised CL to shock (20) before I have a valid OCLT? CL is usually in the 7-10 range when I'm paying attention, but likely has been in the 5-10 range due to tax season (done tomorrow!)
(b) Could it be something other than algae? Copper stain? Would not think that would be slimy to the touch.
(c) If algae but all numbers appear fine, could it be a circulation/brusing problem? Admittedly, I have not been brushing much lately due to tax season, so it is possible that some of those crevices just have not had good movement to prevent those little things from spouting up.

As always, thanks much for the feedback!
 
Green, slimy, and on the walls almost invariably means algae. Stains aren't slimy. Pollen doesn't accumulate on the walls. I would try brushing it off. If it brushes off (perhaps will a little effort) then it just about has to be algae.

With CYA around 50 the minimum FC level is 4, so there shouldn't normally have been a problem. Bad circulation is one possibility. Lower FC levels in the past are another possibility.

It sounds like it is time to shock the pool, with extra attention to brushing throughly.
 
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