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Thread: Black algae stuck to the bottom

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    Black algae stuck to the bottom

    Hello all,

    My question is more about how long I have to keep the shock levels up. I know it's 'until the algae is gone', but wondering about a time line?

    Pulled my solar blanket off on Sunday and found algae stuck to the bottom. Not sure what kind it was, but that's the only place. There were no floating pools of algae or anything like others have described, but probably 70% of the bottom of my pool was black.

    Read all the articles, did everything as per the book and it's no Wednesday. There is some improvement, but is this going to take weeks?

    Levels:

    FC: maintaining around 20, drops to 17 or so over night, back up to 20, drops to 15 during the day back to 20
    CC: 0
    PH: brought to 7.2ish before this process
    TA: 90
    CH: not sure
    CYA: 80

    Using Pool Boss Liquid Chlorine (on my 3rd case now....) to bring up to shock levels and brush it twice a day with a brush that is ~1 month old.

    Thanks to anyone for the advice or help.

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    frustratedpoolmom's Avatar
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    Re: Black algae stuck to the bottom

    What kinda brush? As you have probably read the key to Black Algae is the brushing to expose the roots to chlorine. You keep at it till you can't see the BA anymore. How long you been at it?
    You need to know your CH because you have a plaster pool.
    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
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    Richard320's Avatar
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    Re: Black algae stuck to the bottom

    There's no chance it could just be some kind of staining?
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Black algae stuck to the bottom

    Are you using a regular pool brush or an algae pool brush. An algae brush is metal and is necessary to expose the algae to the chlorine.

    According the CYA/Chlorine Chart: pool-school/chlorine_cya_chart_shock

    The target regular shock level for your CYA is 31. I'm not an expert on the different types of chlorine. Hopefully someone will help you find the appropriate level for your type of algae.

    You might want to consider replacing some water to get your CYA level down. At 80, your CYA is protecting the chlorine from doing its job.
    Karen
    33K IG w spa plaster, Pentair 1HP Whisperflo, DE Filter, SWG CircuPool RJ-60, Dolphin Triton Plus, Raypak Dig 336K BTU, TF-100.
    Pool Math Chlorine / CYA Chart SLAM - Shock Level And Maintain
    2017 replaster/retile

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    Re: Black algae stuck to the bottom

    Thanks for the quick responses.

    Don't think it could be staining. There are clumps where it's a bit thicker and the 'blackness' has gone down.

    I'm using a nylon bristled pool cleaning brush. Will run by the pool store today for the metal bristled one.

    In regards to the shock level, I was using the pool calculator mentioned in the Green Swamp Algae article which says to bring it up to 19-21 based on my stats. Have been using this guidance so questioning if i need to start bringing it up to 30-ish level?

    Thanks,
    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    A CYA value of 80 ppm requires you to maintain about 30 ppm FC (per the FC/CYA chart in Pool School). Until you bring it up there and hold it there, you not really shocking the pool as we suggest.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Black algae stuck to the bottom

    Roger that. Guess I'll pick up another couple cases of Chlorine as well... And start playing around with draining/adding water.

    Thanks for the help.

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    Lowered CYA to 60-65 and bought a metal brush.

    Seems like the algae is slowly retreating. Keeping the FC about 25.

    Now any recommendations? Any ideas on how long this is going to last?

    Thanks,
    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    Any ideas on how long this is going to last?
    I can give you some extremes but it's not very helpful. 3 days to 14 days would be my thinking.

    The more you scoop, brush, filter and vacuum, the less organics the chlorine has to deal with so doing all that work as often as you can and replenishing your chlorine as often as you can will speed the process.

    It also depends on the size of your filter. A filter too small for this big job can be a PITA. A giant filter always speeds things up.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Black algae stuck to the bottom

    Thanks for the help folks. Just got a new set of chemicals in the mail, so re-tested everything except CH (last set about 2yrs old). Not sure if the new chemicals changed the numbers or something else going on. Here's what I get now:

    Tested 21:45 Pacific Time

    FC: 28.5
    CC: .5
    TC: 29
    pH: No clue, haven't tested since last Sunday (read that it wouldn't matter, should I still be adding acid???)
    T/A: 140 (did this go up due to pH going up?? Or due to new chem kit?)
    CH: 500+ (using old kit. I can never get this test right, need a speed stir...)
    CYA: 50 (between 50 and 60 pretty evenly, but closer to 50)

    I'm brushing twice a day with a metal brush. I haven't had algae in the filter basket (have a little nylon thing in it to catch stuff) for a few days now, but still visible clumps of algae on the bottom of the pool. Running the pump 24/7 for now. I must say that things look MUCH better than when I started, but still those stubborn ones left and they don't seem to be moving at all.

    Given the new chem readings, do I need to do anything special? Or just stay the course?

    Thanks again,
    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    Stay the course, Joel. Those numbers look good to me. Yes, disregard the pH and TA until your pool is crystal clear.

    Again, the time frame for clearing out everything can be maddeningly slow but there really is no alternative....just keep on keepin' on.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Black algae stuck to the bottom

    Did the overnight test.... (actually set the alarm to wake up before the sun... **** pool... )

    FC: 24.5

    So lost 4 ppm. I guess that's not bad?

    Adding more chlorine to burn these buggers out....

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    Quote Originally Posted by EvermoreUW
    Thanks for the help folks. Just got a new set of chemicals in the mail, so re-tested everything except CH (last set about 2yrs old). Not sure if the new chemicals changed the numbers or something else going on. Here's what I get now:

    Tested 21:45 Pacific Time

    FC: 28.5
    CC: .5
    TC: 29
    pH: No clue, haven't tested since last Sunday (read that it wouldn't matter, should I still be adding acid???)
    T/A: 140 (did this go up due to pH going up?? Or due to new chem kit?)
    CH: 500+ (using old kit. I can never get this test right, need a speed stir...)
    CYA: 50 (between 50 and 60 pretty evenly, but closer to 50)

    I'm brushing twice a day with a metal brush. I haven't had algae in the filter basket (have a little nylon thing in it to catch stuff) for a few days now, but still visible clumps of algae on the bottom of the pool. Running the pump 24/7 for now. I must say that things look MUCH better than when I started, but still those stubborn ones left and they don't seem to be moving at all.

    Given the new chem readings, do I need to do anything special? Or just stay the course?

    Thanks again,
    Joel
    TA went up when you added fresh fill water when you lowered CYA. That's my guess, anyway.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

  14. Back To Top    #14

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    Re: Black algae stuck to the bottom

    Maybe it's just me, but it seems like I have new clumps of algae forming in places it wasn't before.

    Does that even make sense at these chlorine levels?

    Tested when I got home from work and was at 20. Added half a jug of chlorine, went out for HH and came back 3 hrs later and it was at 20.5.

    Just added a full jug (sun isn't on the pool any longer) and I guess we'll see where we stand at 10p tonight.

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    OK, tonight's test.

    After adding the jug, waited another 3 hours for test.

    FC: 29.5

    We'll see what the morning brings.
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

  16. Back To Top    #16

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    Re: Black algae stuck to the bottom

    Woke up this morning.

    A bit of sun had been on the pool.

    TC: 24.

    Blah.
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    No point in doing the OCLT until you meet the other two things we look for to conclude the shock process....crystal clear water and CC's of .5 ppm or less.

    If you have visible algae, you need to continue shocking, filtering, brushing, etc.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  18. Back To Top    #18

    Re: Black algae stuck to the bottom

    Any update from the original poster?

    I never *quite* got rid of all of my black algae last year and the spots have grown tremendously. I'm shocking the heck out of it and wire brushing as much as I can hold my breath even now. I'm hoping for a good result in the next few days before I get frustrated and start pouring in copper.

  19. Back To Top    #19

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    Re: Black algae stuck to the bottom

    Hello,

    I think I ended up going through 8-10 bottles of chlorine for my pool to keep it at shock levels high enough to do any good. Doing that, magically, everything was gone the 7th day when I woke up.

    It was frustrating because the water never got cloudy so it seemed swimmable and the black spots cleared most of the way, but that last little bit was quite stubborn. Like I said, all gone in 7 days though.

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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    Re: Black algae stuck to the bottom

    Oh, and I should mention that during this process the wife became quite frustrated that the Internet wasn't helping so I went to the pool store to buy some high powered **** that our neighbor said they were sold. Believe me, not what I wanted to do, but to keep the peace....

    Anyway, got to the pool store and told the guy my situation and he completely agreed w what everyone here said and wouldn't sell me a thing. So just keep doing high chlorine at shock levels, and wire brushing.

    Also probably good to understand where your CYA is so you know where your chlorine shock level needs to be. The people on this board a super helpful though if you post your stats.

    Joel
    ----
    Gilbert, AZ
    12,500 gal, 16'x26', 90' perim
    IG; Granite Blue Pebble Sheen
    SWG, Pentair VS3050 pump
    Sta-Rite cartridge filter
    MagnaSweep in ground
    QuickTouch4

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