Seahunt Posted March 30, 2012 Report Share Posted March 30, 2012 I have somewhere around 6 or 8 of these in my deep end. It is a 10 year old plaster pool. They are concave (e.g., a little crater) and will not brush off. Thanks. http://i49.photobucket.com/albums/f285/schmity1/R1-01509-014A.jpg Quote Link to comment Share on other sites More sharing options...
Pool Clown Posted March 30, 2012 Report Share Posted March 30, 2012 Looks like black algae that has taken hold in an imperfection in the plaster surface. Quote Link to comment Share on other sites More sharing options...
Seahunt Posted March 30, 2012 Author Report Share Posted March 30, 2012 Ok thanks. The pool is not yet open as I took these pictures last summer. What do you recommend? Quote Link to comment Share on other sites More sharing options...
waterbear Posted March 31, 2012 Report Share Posted March 31, 2012 For starters posting a full set of test results NOT done with strips. We need free chlorine. combined chlorine, pH , total alkalinity, calcium hardness, and CYA (cyanuriic acid or stabilizer). If you have black algae it usually means one of two things, either the pool was run for a long time at too low free chlorine has had too much stabilizer for a while. Quote Link to comment Share on other sites More sharing options...
Seahunt Posted April 3, 2012 Author Report Share Posted April 3, 2012 Ok. I will post results when I can but the pool is not yet open. As for last year, I tried to raise FC every day to 10% of of CYA. My CYA ran from 40 at the beginning of the year to around 80/90 when I closed it. Does this sound correct? For eliminating the black algea, what is the best method? I've heard it is quite a fight. I'm thinking the brushing and laying trichlor right on the spot (since it is on the botton at the deep end) might be the best method. Thanks again. Will be opening the pool first of May. Quote Link to comment Share on other sites More sharing options...
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