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Thread: Black Algae treatment in drained pool

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    Black Algae treatment in drained pool

    I have a small (10,000ish) gallon concrete pool in Florida. A group of people came to my house right from the ocean and within a few weeks I started seeing black algae forming in the pool. Went to pinch a penny pools and they sold me a stainless steel brush, a qt. of Sun Coast Metal Control. They told me this would help loose up the outer shell/coating of the algae before scrubbing it. They also sold me quart of SUPER BLACK ALGAECIDE for killing the stuff. I did everything just like they told me. Most of it appeared to go away except for a few very small spots that I just couldn't remove. Within a week it started coming back right where it was before and just as bad. I did it all again with the same result. Needless to say, that gets expensive and frustrating. That all may be a little long winded considering my real question. Since my pool is so small, draining it is not an issue. I am wondering what would be my best approach, (other than replastering) to kill this stuff now I can get right to it. Chlorine wash? Acid wash? Something else?

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    Mod Squad YippeeSkippy's Avatar
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    Re: Black Algae treatment in drained pool

    Hi there RFoster, welcome to TFP

    Have you ever purchased your own test kit to keep up on your own pool's health? I would seriously recommend that, and only one of the ones we recommend.

    Next, read this -> Pool School - Black Algae

    STOP using any algaecides as they can contain copper, which you do NOT want in your water. Start reading how we care for pools in the Pool School section and see how we can help you better.

    How are you chlorinating your pool?

    Maddie
    Maddie :) 12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
    Skippy's Pool Cooler --> Skippy's New Fountain Our Build --> Our Pool Solved Our Sloping Yard

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    Re: Black Algae treatment in drained pool

    Welcome to the forum

    Please read "The "ABC's of Pool Water Chemistry" up in Pool School. That'll get you started.

    Why do you think you have black algae? Do you have a pic? It is often misidentified

    I can tell you black algae is NOT brought to a pool from the ocean as you seem to say. It is a pretty long, slow buildup over time that always is a result of inadequate chlorine.

    Once you get it, it's tough to get rid of but you can do it with diligence.

    Read that article and ask lot's of questions.....it's not a quick fix but you will have a new understanding of the cause and the cure if it's black algae.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Black Algae treatment in drained pool

    Sorry I disappeared... Had the dreaded flu.. First off, I think I was not clear that my pool is currently drained.

    I have a test kit, (a pretty simple one). I use liquid chlorine that I get from my local pool supply and they do a full water test with instructions each time i go in which is every 2 weeks. I have never had an issue like this in over 10 years. I think its black algae because it looks like all the black algae pictures and videos I have seen online and it has been resilient to aggressive treatment. As I mentioned, I have not had an issue with the pool in over 10 years. The one and only time I have people over right from the ocean.. this stuff appeared. I have read multiple articles which state it can be introduced from ocean water. Maybe its just a coincidence but seems plausible, I am not a chemistry nor pool expert. Bottom line at this point, is I need to find out the best approach for dealing with it dry. I chlorine washed my pool a few years back but not sure if that would be the best option or acid wash. Or something else. Thanks

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    Re: Black Algae treatment in drained pool

    Typically a pool store aggressive treatment is not really aggressive at all. We raise clorine to shock level for the cya level and mantain untill all algae has been destroyed. We do this with a proper test kit, tf100 or Taylor 2006c, as pool store testing is typically wrong and leads you in circles.

    As what you need to do with a drained pool I'm sorry I'm can't be much help, someone will be along soon enough.
    Casey
    Intex 24' x 52" closed for winter 2018, 2 Main Drains, 1 Skimmer, 1 Return, PVC
    1/2 HP Intex Pump 633T w/ Taeglus TA-40 175 lb 19.5" Sand Filter, Auqabot Extreme Robot
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    Re: Black Algae treatment in drained pool

    rfoster143, sorry to tell you but you're getting ripped off, their testing and instructions are designed for one thing, to keep you coming back every two weeks.

    It's interesting they gave you this line about using a 'Metal Control' product to help loosen the algae, complete nonsense. yes the brushing will help do that but they sold you the Metal Control because in they knew in the next step they were going to sell you an algaecide loaded with copper.
    20' X 40' IG vinyl lined; 31,300 gallons; built ~30years ago
    Hayward 1HP Single Speed Pump w/Sand Filter
    Taylor K-2006,Rola-chem sodium hypo feeder/ 15 gallon tank
    Fill from soft/neutral well water, low flowrate well pump

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    HiddenRiver's Avatar
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    Re: Black Algae treatment in drained pool

    Rfoster143–I felt your pain this past summer. The TFP method worked much bettter than the PS recommendations and costly concoctions. All you need is cheap chlorine bleach you can get at Walmart and lots of it, along with your very own test kit that will provide you accurate results (not the pool store or test strips). It is worth the investment. Since your pool is drained maybe there is another way to apply chlorine directly on the algae and brush, but I don’t know what that is. Good luck with it all! It takes diligence and likely at least two weeks of it!
    40,400 inground gunnite, max depth 10-ft with 1.5 hp single speed Pentair, DE filter, well water, only one skimmer working, TAYLOR TK-2006 TEST KIT COMP CHLORINE FAS-DPD, Chester County, PA--OLD pool, but a beauty.

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    Re: Black Algae treatment in drained pool

    Thanks for all the responses. I have this same post at another pool site and somebody suggested using chlorine dioxide. Anybody know anything about this product and its use?

    Seems the general thought is my pool supply folks are idiots. When I go in they have the entire chemistry set up with computer results etc.. So I figured they knew what they were doing..... I never put it together they were selling me a metal removing product then having me put a metal inducing product in right after.

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    JoyfulNoise's Avatar
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    Re: Black Algae treatment in drained pool

    There is no chlorine dioxide product that is approved for pool use. Chlorine dioxide is typically used in wastewater treatment facilities as an initial sanitation treatment (but not a residual treatment as that is left to chlorine/monochloramine) and it is usually generated on site. There are also water purification tablets that hikers use that are based on chlorine dioxide but those are actually composed of sodium chlorate and an acid catalyst. The tablet dissolves in water and the two chemical components react in-situ to create chlorine dioxide. Chlorine dioxide is highly unstable towards UV oxidation and so it could not be used in a pool as daylight would destroy it quickly. Some have postulated that it could be used as an overnight treatment for water disinfection and clarification, but no product has ever been sold partly because it would have to undergo rigorous testing to be classified as a disinfectant/sanitizer for pool use and that's a very expensive process.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Black Algae treatment in drained pool

    Quote Originally Posted by JoyfulNoise View Post
    There is no chlorine dioxide product that is approved for pool use. Chlorine dioxide is typically used in wastewater treatment facilities as an initial sanitation treatment (but not a residual treatment as that is left to chlorine/monochloramine) and it is usually generated on site. There are also water purification tablets that hikers use that are based on chlorine dioxide but those are actually composed of sodium chlorate and an acid catalyst. The tablet dissolves in water and the two chemical components react in-situ to create chlorine dioxide. Chlorine dioxide is highly unstable towards UV oxidation and so it could not be used in a pool as daylight would destroy it quickly. Some have postulated that it could be used as an overnight treatment for water disinfection and clarification, but no product has ever been sold partly because it would have to undergo rigorous testing to be classified as a disinfectant/sanitizer for pool use and that's a very expensive process.
    That's a very informative post. Thank you. Just want to make it clear.. and still not sure how i would use it.. that my pool is dry/empty. I would not use this in a filled pool. I have a concrete/plaster pool and want to kill it dry.

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    Re: Black Algae treatment in drained pool

    A bleach scrub and power wash should be sufficient. You really don’t want to leave a plaster pool empty for too long. Allowing the plaster to remain dry lowers its life expectancy.

    Black algae really isn’t something that you can easily kill on a drained pool. The microscopic roots can go deep enough into the plaster to avoid surface cleaning. What takes care of black algae is consistent, higher levels of FC and not ever allowing the FC to go lower than minimums. Only over time can the FC exposure kill the algae. You can also try keeping the phosphates low in hopes of starving it of the nutrients it needs to grow and/or using borates in your pool water as they act as a mild algae inhibitor. Don’t mess around with bromine or copper algaecides as they will lead to all sorts of secondary problems.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Black Algae treatment in drained pool

    Quote Originally Posted by rfoster143 View Post
    That's a very informative post. Thank you. Just want to make it clear.. and still not sure how i would use it.. that my pool is dry/empty. I would not use this in a filled pool. I have a concrete/plaster pool and want to kill it dry.
    I don’t know about Chlorine dioxide but if it is used for drinking water treatment it might be expensive for a large pool. Whatever you use it must kill the spores. This is why it is so difficult to eradicate. It may Also not be a one step process. My thought is (I am not an expert) if you want to work “in the dry” first is wire Brush the inside of the pool (brushing is important because of the filaments of the algae that penetrate the plaster) then wash down with a chlorine bleach and water mixture (so the fumes don’t kill you). Then when you fill the pool back up SLAM again and then keep your chlorine levels a little higher than normal to be sure it is all killed for the entire swimming season. I am thinking this year I will do the same just in case some spores have survived somewhere.
    40,400 inground gunnite, max depth 10-ft with 1.5 hp single speed Pentair, DE filter, well water, only one skimmer working, TAYLOR TK-2006 TEST KIT COMP CHLORINE FAS-DPD, Chester County, PA--OLD pool, but a beauty.

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    Re: Black Algae treatment in drained pool

    Quote Originally Posted by JoyfulNoise View Post
    A bleach scrub and power wash should be sufficient. You really don’t want to leave a plaster pool empty for too long. Allowing the plaster to remain dry lowers its life expectancy.

    Black algae really isn’t something that you can easily kill on a drained pool. The microscopic roots can go deep enough into the plaster to avoid surface cleaning. What takes care of black algae is consistent, higher levels of FC and not ever allowing the FC to go lower than minimums. Only over time can the FC exposure kill the algae. You can also try keeping the phosphates low in hopes of starving it of the nutrients it needs to grow and/or using borates in your pool water as they act as a mild algae inhibitor. Don’t mess around with bromine or copper algaecides as they will lead to all sorts of secondary problems.
    JoyfulNoise I responded before seeing your post. Sorry about that!
    40,400 inground gunnite, max depth 10-ft with 1.5 hp single speed Pentair, DE filter, well water, only one skimmer working, TAYLOR TK-2006 TEST KIT COMP CHLORINE FAS-DPD, Chester County, PA--OLD pool, but a beauty.

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