I have had some small dark spots in the shallow end for about one month now. They won't come off when brushing with a metal algae brush so I got a mask, snorkel and pumice stone and went to work on them individually. I noticed that these dots looked more brown than black to me. - even when they smeared they still looked brown - not green. I am try to figure out if this is black or green or mustard algae .
I put a fortune's worth of bleach into this ingroud plaster pool and brushed it regularly,. The little dots are barely noticeable but I am losing quite a bit of chlorine at night time. I cant pass the OCLT test. The pool itself looks pretty darn good but I FEEL That I am not making any progress on whatever is living in the pool.
I tried scraping the spots iwth a tri-chlor puck too,
Any other advise?
15000 Gal. In Ground Plaster