Brown Algae?

[robmaxfli]

Hi Folks,
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
ph- 7.2
FC 12-25ppm
CYA -30

 

[JasonLion]

All kinds of algae except black algae brush off. And even black algae will partially brush off. If a steel brush is not affecting the spot, it isn't algae.

Brown spots sound like iron stains. Try holding a vitamin C tablet against one of the spots for 30 seconds and see if that does anything.

 

[robmaxfli]

I tried the Vitamin C tablet against it and it did not affect it. I lose quite a bit of chlorine at night so that is why I was thinking it could be algae.
The pool looks great but the walls and floor do feel slippery to the touch. When I brush the pool I can always see "dust " from my brush stroke.

 

[jblizzle]

Sounds like you have not completed the ShockLevelAndMAINTAIN Process yet if you can not pass the OCLT and the pool feels slimy.