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Thread: Possible Black Algae

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    Possible Black Algae

    I just came home from 3 weeks away. When I left pool was clean , clear good chlorine number and PH balanced. After vacuuming ...I noticed lots of black spots scattered all over the bottom of my pool. Brushing in the usual manner did not remove them. My test results are as follows

    FC 2.5
    PH 8.3
    TA-70
    CH-310
    CYA-50
    Salt 2800

    We had two days of drenching rain while I was away ( over 5 inches of rain)

    Immediately added bleach to raise my chlorine to the high side of normal for my CYA.

    My concern is black algae....I read the page on how to treat it and scrubbed like crazy this morning on all the spots I can reach...the ones in the center I can't reach ...I'm going to follow the suggested steps for the next 3 days but then I have to travel for work again.

    What other steps should I take and in what order should I try and get my other chemicals back up to proper levels.
    I have already raised chlorine ....added acid to adjust PH and put in salt . I also noticed my SWG was set at a much lower percentage than I usually keep it....which may have contributed to the much lower chlorine levels..along with the dilution of salt due to rain.

    Thank you
    Ps- I also noticed a whole lot of gravel from my roof all over the pool deck ...my roof is needing to be replaced soon and I'm constantly cleaning up the stones and vacuuming them from pool...could this be the cause of the spots? Since they sat on bottom for a long time? Anyway to confirm Black Algae?
    12,000 gallon plaster pool
    SWG pool pilot Nano
    Cartridge filter
    South Florida / under screen cage south facing
    TF-100

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    duraleigh's Avatar
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    Re: Possible Black Algae

    Welcome to the forum. Black algae tends to develop in a pool that has been badly neglected for a pretty long period of time.

    So, if you have been maintaining proper chlorine steadily the chances are VERY VERY slim that is black algae. That said, I don't know what it is.

    PS - Your pH is wa-a-a-a-y too high.....get it down to about 7.5 sooner rather than later.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad woodyp's Avatar
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    Re: Possible Black Algae

    You can scratch the top of a suspect black algae spot and then see if it is either slimy to touch or reveals green underneath.
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    Re: Possible Black Algae

    Quote Originally Posted by duraleigh View Post
    Welcome to the forum. Black algae tends to develop in a pool that has been badly neglected for a pretty long period of time.

    So, if you have been maintaining proper chlorine steadily the chances are VERY VERY slim that is black algae. That said, I don't know what it is.



    PS - Your pH is wa-a-a-a-y too high.....get it down to about 7.5 sooner rather than later.
    Adding acid was the 2nd thin I did after raising the Chlorine with bleach...my PH always creeps up here...I usually treat it once a week...the long period away let it creep up higher.

    I started flowing this program after a bad algae bloom two years ago in the spring...I truly have had a trouble free pools since then...until now..

    Some spots lightens or went away with serious bushings...others are still there.

    I have raised chlorine to 6.... And will keep scrubbing the spots I can reach several times a day for then next 3 days and see where I get.

    - - - Updated - - -

    Quote Originally Posted by woodyp View Post
    You can scratch the top of a suspect black algae spot and then see if it is either slimy to touch or reveals green underneath.
    All the spots are on the bottom and I can't reach them except with a brush on a pole. They are also very small.....
    12,000 gallon plaster pool
    SWG pool pilot Nano
    Cartridge filter
    South Florida / under screen cage south facing
    TF-100

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    Mod Squad jblizzle's Avatar
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    Re: Possible Black Algae

    A chlorine level of 6ppm is no where near high enough to deal with algae. You need to maintain a FC level of 20ppm bases on your CYA level of 50ppm and completely follow the ShockLevelAndMAINTAIN Process
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Re: Possible Black Algae

    Quote Originally Posted by jblizzle View Post
    A chlorine level of 6ppm is no where near high enough to deal with algae. You need to maintain a FC level of 20ppm bases on your CYA level of 50ppm and completely follow the ShockLevelAndMAINTAIN Process
    I read here
    http://www.troublefreepool.com/content/180-Black-Algae
    That a SLAM is not how you deal with Black Algae

    I know I need to raise my chlorine some more...I was just asking in what Oder I should correct what is off....I raised the chlorine to the high end of normal...then stared on getting PH back down...should I leave my CYA alone for now? I usually keep it above 60 as re come deD for a SWG pool.
    12,000 gallon plaster pool
    SWG pool pilot Nano
    Cartridge filter
    South Florida / under screen cage south facing
    TF-100

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    Mod Squad jblizzle's Avatar
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    Re: Possible Black Algae

    Well, I would try to confirm what it is you are seeing in the pool. Post up pictures. If you scrap off some of the black and smear it on a piece of paper is it green?

    I would not raise the CYA or the salt until we know if you need to SLAM the pool or not.

    I would have lower the pH first and then raise the FC level.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  8. Back To Top    #8

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    Re: Possible Black Algae

    I'm not sure how to scrape any off....it is all on the bottom of pool and I can't reach it. I tried to take some photos....but it's sunny and windy so I can't get a picture that you can see anything.

    Thanks for your help...I tested pH again today after adding acid yesterday...ph is now 7.6.
    12,000 gallon plaster pool
    SWG pool pilot Nano
    Cartridge filter
    South Florida / under screen cage south facing
    TF-100

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    Mod Squad jblizzle's Avatar
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    Re: Possible Black Algae

    You are in FL ... swim down and scrap some off
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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  10. Back To Top    #10

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    Re: Possible Black Algae

    That won't work ....I'm blind as a bat without my glasses and I can't see a thing.....spots are so small I couldn't find them .besides I may live in Florida...but to me it's still early spring and my water is still way too cold to get in.

    - - - Updated - - -

    So...tell me what's the deal.....do I slam or not? I've seen conflicting posts here. I leave for 5 days again on Wed...so I'll keep chlorine above normal and keep brushing before I go....then can do a full slam when I get back.

    Here is another question....you refer to a stainless brush...my brush has stainless and nylon.....that was all my local store had...are there other all stainless brushes?
    12,000 gallon plaster pool
    SWG pool pilot Nano
    Cartridge filter
    South Florida / under screen cage south facing
    TF-100

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    Mod Squad jblizzle's Avatar
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    Re: Possible Black Algae

    There are full stainless brushes, although what you have should work.

    I do not think you have definitely identified the problem to know the proper path forward. Just keep the FC elevated and scrub a bunch before you leave.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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    Mod Squad kimkats's Avatar
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    Re: Possible Black Algae

    Can you get a puck onto a spot that has several of the spots? If so see what happens........


    SLAM? I would bring your levels to high levels until you leave but am unsure about you doing a SLAM. I will let someone else answer that one.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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