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Thread: Black Algae

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    boston62's Avatar
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    Black Algae

    how does this grow in a balanced pool, I have these black dots showing up, not many but maybe 5 to 10? Doesn't chlorine kill this type of algae?

    Thanks
    13,000 Gal Pool & Spa
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    Re: Black Algae

    We need to know your test results before that question can be answered.

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    Re: Black Algae

    Fc. 8.5
    cc 0
    ph 7.6
    ta 75
    ch 350
    cya 70
    13,000 Gal Pool & Spa
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    Re: Black Algae

    It doesnt look like algae, doesn't rub off.
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    Re: Black Algae

    Are you sure they are in fact black algae? Do they have what appears to be legs growing off them?

    Try placing a VIt C tab on them, if that doesn't work, try some dichlor for a short time. Do not leave the Dichlor on it for long though.

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    Re: Black Algae

    I tried the vit c & the puck, nothing happens...I think tomorrow I'll take a picture.
    13,000 Gal Pool & Spa
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    Re: Black Algae


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    Re: Black Algae

    Yes I read that info, been using the steel brush on them. Thanks for the help will keep an eye on it.
    13,000 Gal Pool & Spa
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    Re: Black Algae

    Here is a photo of one spot.
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    Re: Black Algae

    Hard to say if that's algae or a stain. If you scrape some of it off and smear it on a white piece of paper, then if it's green or dark green, then it's black algae for sure. That would normally only grow in a pool with proper FC/CYA levels if the circulation in that area were very poor. You'd also want to completely get rid of it at its roots by scraping it off and exposing it to high chlorine level. A Trichlor puck would do that, but would also likely leave a mark on your pool surface and you've got such a nice looking surface I wouldn't want to ruin it.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Black Algae

    Its not soft but hard like a rock, even after scraping it with wire brush. Will not scrape off..
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    Re: Black Algae

    I put a vit c tablet on it nothing happend, then the puck left for 2 hours nothing...wish I knew what it was.

    The only thing I can think of from using MA or some other chemicals brought it out from the plaster finish.
    13,000 Gal Pool & Spa
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    Re: Black Algae

    You sure it is not just a black stone in the plaster, like all the blue ones?

    Oh, did you say that they just showed up and were not there before?
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    Re: Black Algae

    Quote Originally Posted by jblizzle View Post
    You sure it is not just a black stone in the plaster, like all the blue ones?

    Oh, did you say that they just showed up and were not there before?
    They were not there before they just started showing up, when I had a pool man taking care of it before TFP they were not there but the FC was at 16 and CYA was over 100. When I started to take over I added the swg..then since March 2014 they started showing up..They look like stone, but what made them show up...Thank you
    13,000 Gal Pool & Spa
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    Taylor (FAS-DPD K-2600, Pool Surface: Plaster

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    What could I have done wrong..

    Merged by moderator. Please keep all related questions discussion in the same thread. jblizzle

    When I took over the pool from the pool man, I had no algae, at that time FC was 16 according to pool store. This all before getting my test kit and TFP.

    Now the pool FC has never been below 5, and balanced... Now I have started getting black spots started with 1 or 2 now about 10, just trying to see if I did not take care of pool right. I have been steel brushing algae spots...The pool does look great except these growing spots.

    Thank you
    13,000 Gal Pool & Spa
    Jandy Automation /w IAqualink
    Autopilot SWG
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    Taylor (FAS-DPD K-2600, Pool Surface: Plaster

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    Re: What could I have done wrong..

    As you should know by now, questions like this one need to be accompanied by a full set of water test results. Without that additional information it is impossible for us to help you.

    Also, do these black spots brush off?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: What could I have done wrong..

    Jason sorry about that..

    FC 8
    CC 0
    PH 7.6
    TA 75
    CYA 70
    Salt 3300

    They do not brush off with steel brush, 3 " tablet, or vitamin c... They seem to just appear..

    I did add a swg & Jandy VS Pump.
    13,000 Gal Pool & Spa
    Jandy Automation /w IAqualink
    Autopilot SWG
    Jandy 2.0 HP VSP, Filter Cartridge
    Taylor (FAS-DPD K-2600, Pool Surface: Plaster

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    Re: What could I have done wrong..

    Can you scrape them with your fingernail and get a dark greenish cast when rubbed on a white sheet of paper?

    That would indicate black algae, but based on your description, I would doubt that's what it is and I doubt it will scrape off.

    I would suspect it is some kind of mineral deposit.

    Got a pic?
    Dave S.
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    Re: What could I have done wrong..

    I just don't think I did anything wrong...but will watch it. Thanks
    13,000 Gal Pool & Spa
    Jandy Automation /w IAqualink
    Autopilot SWG
    Jandy 2.0 HP VSP, Filter Cartridge
    Taylor (FAS-DPD K-2600, Pool Surface: Plaster

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    Re: Black Algae

    How does one get mineral deposits, is it a staining, but most of all how to cure it, and find the source.. Thank you
    13,000 Gal Pool & Spa
    Jandy Automation /w IAqualink
    Autopilot SWG
    Jandy 2.0 HP VSP, Filter Cartridge
    Taylor (FAS-DPD K-2600, Pool Surface: Plaster

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