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Thread: Black algae?

  1. Back To Top    #1

    Join Date
    May 2007
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    Black algae?

    Good afternoon Good Folks!!

    Old member here, and thanks to the good folks here my pool has been doing pretty good.

    On and off (mostly on), I've been having what seems to be more and more spots of algae in my pool. They're black, about the size of a pencil eraser, come off with a little scrubbing, seem to prefer steps and sun decking, but seemed to be like the bottom in the shallow end lately.

    I had run out of the powder to measure my chlorine acurately, but the blue kit showed me at 2+ all summer... got me some new powder this week and here's my numbers as of yesterday:

    Thanks in advance for your help!!

    FC 4
    CC 0.5
    TC 4.5
    pH 7.7
    T/A 100
    CH 200
    CYA 40
    Temp 85F
    Borates 30 (probably has been higher, but good bit of rain lately)
    18,000 gallon gunite free form, with spa, 4x160, EasyTouch, SWCG, Pentair cartr filter, Colorlogic lights.

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    frustratedpoolmom's Avatar
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    Re: Black algae?

    Can you post a pic?

    If it's black algae, the trick is constant brushing of the "heads" while at elevated chlorine levels - the brushing knocks off the protective outer shell, so that the chlorine can get to the inside and destroy it.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  3. Back To Top    #3

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    Re: Black algae?

    Hey MOM!

    I'll try to get some pics this afternoon.

    How elevated do I need to get the chlorine, and how long you think?

    That's one thing that I haven't done is continually brush them... then again... that's why I'm here... so I can get focused!
    18,000 gallon gunite free form, with spa, 4x160, EasyTouch, SWCG, Pentair cartr filter, Colorlogic lights.

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    frustratedpoolmom's Avatar
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    Re: Black algae?

    Well, I would say raise it up to shock once, then keep it at your normal "target" level for a couple of weeks while you brush daily, then after a couple of weeks, do an overnight loss test and make sure there is nothing alive....
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    reebok's Avatar
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    Re: Black algae?

    if it is black algae I would advise what FPM has said in other posts, to rub a trichlor puck over them (after brushing, if you have any pucks). worked like magic for me.
    16x32 21,000 gallon in-ground exposed aggregate, 1.5hp pump, 120 sqft catridge filter, birdcage, solar panels, aquavac tigershark qc robot.

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    frustratedpoolmom's Avatar
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    Re: Black algae?

    IF the BA is dead, the pucks should work to remove the stain. But if the BA is alive, that might not be enough. You can give it a try though.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  7. Back To Top    #7

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    Re: Black algae?

    well... pool is in kill mode, and algae is in dieing mode (I think)

    brushed every spot of it I could find, wiped/scrubbed those areas with trichlor puck, and loaded pool up with chlorine... that was Monday afternoon...

    I threw in some granular chlorine to get it going, and got generator on 100%... checked it few times on the blue kit... its high... and no signs of regrowth.

    so Monday night, all day Tuesday, Tuesday night... so far

    any idea how long that stuff (black algae) can survive massive chlorine intake?
    18,000 gallon gunite free form, with spa, 4x160, EasyTouch, SWCG, Pentair cartr filter, Colorlogic lights.

  8. Back To Top    #8
    frustratedpoolmom's Avatar
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    Re: Black algae?

    It's not the massiveness of the chlorine dose, it's the constant brushing while FC is elevated that will kill it.

    Stick with liquid chlorine for shocking, I wouldn't recommend running the generator at 100%.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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    Butterfly's Avatar
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    Re: Black algae?

    Jus checking: Are you using an algae brush?
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  10. Back To Top    #10

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    Re: Black algae?

    Guess I should be more accurate on my actions...

    For the first day, (actually about 12 hours), ran my generator on 100%,

    second day, Tuesday (about 10 hours), ran my generator on 80%,

    third day, brushed pool this morning, Wednesday, tested water, was at 8.0 ppm Chlorine (so I backed generator down to 50%, for 10 hours)... tested this afternoon, (also note, much areation), 8.5 ppm. oh yea, pretty good rain storm here too... (not sure how much, as I wasn't home)

    no algae brush... just the same old stainless steel brush that I don't use often enough to brush my pool.

    unless suggested otherwise... plan to brush again in a few minutes, and back down generator to about 25% tomorrow, and measure tomorrow evening... slowly taper off, and try to make sure Cl is dropping at anticipated rates... not accelerated algae eating rates...

    Suggestions?
    18,000 gallon gunite free form, with spa, 4x160, EasyTouch, SWCG, Pentair cartr filter, Colorlogic lights.

  11. Back To Top    #11
    frustratedpoolmom's Avatar
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    Re: Black algae?

    You should see visible improvement every day. If the algae comes back, you haven't killed it and you should shock again, repeating the brushing process.

    In the future, it's better to shock with liquid chlorine or bleach, and then use the SWG to maintain shock. It's not a good idea to use the SWG to raise it up to shock level, it can't produce the chlorine fast enough, it's hard on the cell too.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

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