Last November 2009 -January 2010 we had some black algae in one pool. The pool walls are somewhat pebbe type or like we say it here "washed sand walls".
A year ago, we shocked the pool following some hints you have over here and it worked good as the algae kind of dissipated. But it is the first time with the pool at summer time (around 100's now) and our friendly algae is back!
All this time we kept the chlorine levels stable and sometimes higher (FC between 5 & 8) for a 11,000 gal. pool. Water today is crystal clear, swimmable, etc., but in the last three weeks we got the pool a little busy + the rise on the temp to find out that the pool walls seemed not be properly sealed when it was finished therefore it has lots of "orifices" (small ones, but not normal on a nice pebble standard pool) and it is THERE where our fellow blacky is hiding and living!!
We took some samples and they are as thick as a noodle thin pasta (sorry, but my first though was "looks like mice poop!")...
During the last process about a year ago, we shocked the pool for several days as this "blacky" was expanding on the walls slowly until we thought we got rid of it...
So now, it seems it has adapted to the chlorine level from the pool?? and I am wondering if there is any special chemical that can be used to get rid of it?
We have suggested to the pool owner to also do the "resealing" work for the walls, but we don't know if that will happen.
Is there anything I can do about it?