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Thread: Suggestions needed - to fight black and possible mustard algae this weekend

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    Suggestions needed - to fight black and possible mustard algae this weekend

    My salt cell went bad and I had several weeks of time with close to zero FC in my pool. First I got greenish/yellowish algae covering the deep end of the wall and floor. I was able to brush it off with vinyl brush. But the algae came back in a few days. In my pass two weeks, I start to notice back spots and patches on the floor of the deep end. I suspect it's black algae.

    5 days ago, I brushed and vacuumed the pool and kept FC leve between 4 and 5 and the greenish/yellowish algae did not come back. Water is clear. Do I likely have mustard algae in this case? I hope I just have regular green/yellow algae.

    My water test results
    FC = 4.5
    PH = 7.5
    CYA = 70
    TA = 120
    CH = 300

    I am planning to fight black algae this week and want some advise. This is what I plan to do
    1. Dump bleach to the deep end of pool and get FC level to 40 and hold it for 24 hours; use metal brush to brush the pool a few times during this 24 hour period -- to fight black algae and mustard algae if I have it
    2. After the 1st 24-hour period, I will keep the FC level above 20 and brush the black agle area a couple times a day -- to fight black algae

    I have a couple questions -
    1. Should I run the pump non stop during the SLAM period? Or should I let the pump to rest for a few hours every day?
    2. When do I lower the FC level back to 10 (high end of normal)? After all black spot are gone?
    3. Should I turn off the salt cell during the SLAM process?


    Thanks a lot!
    Attached Images Attached Images
    Fremont, CA
    16K plaster IG pool with spa
    cartridge filter, SWG, solar heat

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    Mod Squad jblizzle's Avatar
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    Your FC is way too low for your CYA level. You need to follow the ShockLevelAndMAINTAIN Process.

    What you laid out is NOT the correct process.

    To answer your questions:
    1. Yes let the pump run 24/7 the entire time
    2. After you pass the 3 criteria to stop the SLAM process
    3. Ideally yes, leave the SWG off.

    I would start with the normal SLAM and review the Pool School - Black Algae article.
    Jason, TFP Moderator
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    Quote Originally Posted by jblizzle View Post
    You FC is way too low for your CYA level.
    Cough,SWG,Cough

    You will need to SLAM as jblizzle said, please follow the standard instructions and make sure you brush plenty at SLAM level. From there the Black Algae guide posted will help if it doesn't start to go away from the SLAM. If you have difficulty getting rid of it or it returns after a successful SLAM then you may need to raise your FC target up a couple points and see if that helps. There are other options available if none of that works, but first thing first, start your SLAM.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    Thanks for pointing out my mistakes. I will start the SLAM first with FC up to 28 (based on CYA=70) and maintain the level until CC<0.5 and pass OCLT. Also metal brush often during the period.

    A couple more questions:
    1. Based on the fact that the yellow-greenish algae did not reappear in 3 days now at FC=4.5, can I say it was probably NOT mustard algae?
    2. Some article mentioned that pool light needs to be removed in the algae removal process. Should I do that? I don't know how to remove the pool light under water yet.
    3. Based on the FC/CYA chart, the target FC=5 for SWG. What FC level should I maintain after the SLAM?

    Thank you!
    Fremont, CA
    16K plaster IG pool with spa
    cartridge filter, SWG, solar heat

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    Mod Squad pooldv's Avatar
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    Yes, remove the pool light and scrub the light and the niche. One screw at 12 o'clock and a tab at 6 o'clock. Remove screw and tip it out. You are removing the light capsule, it will float so hang on to it. There should be enough cord rolled up behind it to move it to the deck on a towel.

    5 or 6 is fine for FC after SLAM. I like a little extra, just in case.
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    Mod Squad jblizzle's Avatar
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    Mustard algae is much rarer than people seem to think.

    What I meant about the FC being too low, was that it was not high enough for the SLAM, which I misread and thought you had started 5 days ago. After you complete the SLAM, a FC level of 4.5 should be fine, or a little higher.
    Jason, TFP Moderator
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    I removed my pool light last weekend and found excessive calcium build up in the light niche. I was able to use a screw driver to break off a little, but not much. What's a good way to remove calcium buildup underwater?
    Also, do I have to remove these buildup in the light niche? Will it slowly dissolve and increase my CH level in the long term? Thanks.
    Fremont, CA
    16K plaster IG pool with spa
    cartridge filter, SWG, solar heat

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    Mod Squad jblizzle's Avatar
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    Re: Suggestions needed - to fight black and possible mustard algae this weekend

    If it is out of sight I would ignore it completely. It will not affect your chemistry.
    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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