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Thread: Dreaded Black Algae

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    IkeRay's Avatar
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    Dreaded Black Algae

    It slowly started earlier in the summer when the wife and I went on vacation for a week and used cal-hypo in a floater to maintain the pool. When we got home, the cal-hypo was completely gone and the pool was still blue, but there was signs of algae growth on the flat parts of the steps. I brushed it with a nylon brush and put some bleach directly in that area and it went away pretty much.

    The following month we had to leave town for a couple of weeks for a family emergency and there was no way to maintain the pool while away, so I put the normal cal-hypo floater in and prayed it wouldn't be too far gone when we returned.

    Came home to a pool that was quite green, but came back in <24 hours with 6 gal bleach. Except, in the shallow end (the steps and a corner that gets lots of sun) there was black algae. I attempted to keep this one at bay the same fashion but it seems to be spreading. I am now pouring about 2 gal bleach in every 6 hours and brushing with a steel brush and its not reseeding. I stole a tri-chlor tablet from my brother and let it sit on the stairs where the algae was and ate it up, meaning I have black algae (?).

    I have since dropped that tablet into the shallow end where the algae is most prevalent and go out and push it around with the pool brush every 30-45 min, and it seems to be eating away at the algae, but only at small chunks. I am almost to the point where I want to go buy a bucket of tri-chlor and drop the tablets all over the shallow and let them have at it, but I was wondering if granular dichlor would do just as well there?

    what is the easiest and most cost efficient way to get rid of black algae? would it help if I covered that area of the pool with a tarp so the sun doesn't eat up as much chlorine? how much would it hurt to put granular chlorine across the shallow end where the algae is and let it sit for 2-4 hours and brush it away?
    30,000gal In-ground Gunite Pool DE filter
    Polaris 380 APC

    BBB method all the way - Newb, like to absorb info and chatter, but take the experts' advise

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    Re: Dreaded Black Algae

    Need your test reading. FC CC TC and PH atleast. We need to know where you are in your tests.

    Also, read this thread.

    black-dots-algae-on-the-bottom-of-the-pool-t8817.html?hilit=black%20algae
    Hotrod30

    20 X 40 foot vinyl Borates and Salt Pool
    Rolachem Chlorine Feeder
    Hayward 27 inch sand filter with 80 lbs of pea gravel
    Jacuzzi Splash Pak SP55 DE filter in parallel
    Pentair VF3050 pump

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    IkeRay's Avatar
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    Re: Dreaded Black Algae

    From the deep end (away from the algae):

    FC 3.0ppm
    CC <.5ppm
    CYA 35ppm
    pH 7.6
    TA 170 (I know, its high)

    where the algae is

    FC 0.0ppm
    CC 0.0ppm (nothing is registering)
    CYA 35
    pH 7.7
    TA 170
    30,000gal In-ground Gunite Pool DE filter
    Polaris 380 APC

    BBB method all the way - Newb, like to absorb info and chatter, but take the experts' advise

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    Re: Dreaded Black Algae

    IkeRay.... you got no chlorine in the pool. To fight black algae you need to get atleast 25ppm of chlorine. Go get 5 gal of 12% chlorine and dump it all in the pool. Then brush the walls and floor of the pool. Every 6 hours, take a reading of the FC and bring it back to atleast 25 ppm. Brush the whole pool and the places where the algae is twice. Tomorrow keep the FC up and brush the pool twice and the places where the algae twice again. Then let your FC drift back to 6 or 7 ppm.



    When it is dark outside tonight, come on to this site and do a search for black algae and read.

    Also go here to to figure out how much chlorine you need

    http://www.poolcalculator.com/


    Once black algae takes hold, your in for alot of work.

    Also read these threads:
    need-help-with-black-algae-t4030.html?hilit=black%20algae

    still-brushing-and-shocking-black-algae-should-filters-run-t5952.html?hilit=black%20algae
    Hotrod30

    20 X 40 foot vinyl Borates and Salt Pool
    Rolachem Chlorine Feeder
    Hayward 27 inch sand filter with 80 lbs of pea gravel
    Jacuzzi Splash Pak SP55 DE filter in parallel
    Pentair VF3050 pump

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    Re: Dreaded Black Algae

    Quote Originally Posted by IkeRay
    I have since dropped that tablet into the shallow end where the algae is most prevalent and go out and push it around with the pool brush every 30-45 min, and it seems to be eating away at the algae, but only at small chunks. I am almost to the point where I want to go buy a bucket of tri-chlor and drop the tablets all over the shallow and let them have at it, but I was wondering if granular dichlor would do just as well there?

    what is the easiest and most cost efficient way to get rid of black algae? would it help if I covered that area of the pool with a tarp so the sun doesn't eat up as much chlorine? how much would it hurt to put granular chlorine across the shallow end where the algae is and let it sit for 2-4 hours and brush it away?
    As was just posted, you need to get the overall chlorine level way up in your pool to shock level (even to yellow/mustard shock level) and keep it there while frequently brushing the black algae to remove the slime layer and expose the algae itself to the chlorine.

    The Trichlor tabs on the surface works OK for plaster surfaces though it does generally leave a mark when you are done if you leave it in one place (it bleaches out the plaster and is very acidic so dissolves some of the plaster and you can notice a difference). The high chlorine levels from the Trichlor will locally kill the algae faster, but with the side effect just mentioned. It will also increase your CYA level somewhat depending on how many tablets you use. You cannot use Dichlor for this purpose since it dissolves too readily in the water -- Trichlor is actually better for that "concentration" purpose though you may need to rub it in.

    Keeping the overall pool at shock level and having patience with regular brushing is the best way to get rid of the black algae. The Trichlor method is mostly for the impatient -- the regular brushing with exposure to high chlorine levels is the most important factor.

    Richard
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    IkeRay's Avatar
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    Re: Dreaded Black Algae

    Quote Originally Posted by chem geek
    Quote Originally Posted by IkeRay
    I have since dropped that tablet into the shallow end where the algae is most prevalent and go out and push it around with the pool brush every 30-45 min, and it seems to be eating away at the algae, but only at small chunks. I am almost to the point where I want to go buy a bucket of tri-chlor and drop the tablets all over the shallow and let them have at it, but I was wondering if granular dichlor would do just as well there?

    what is the easiest and most cost efficient way to get rid of black algae? would it help if I covered that area of the pool with a tarp so the sun doesn't eat up as much chlorine? how much would it hurt to put granular chlorine across the shallow end where the algae is and let it sit for 2-4 hours and brush it away?
    As was just posted, you need to get the overall chlorine level way up in your pool to shock level (even to yellow/mustard shock level) and keep it there while frequently brushing the black algae to remove the slime layer and expose the algae itself to the chlorine.

    The Trichlor tabs on the surface works OK for plaster surfaces though it does generally leave a mark when you are done if you leave it in one place (it bleaches out the plaster and is very acidic so dissolves some of the plaster and you can notice a difference). The high chlorine levels from the Trichlor will locally kill the algae faster, but with the side effect just mentioned. It will also increase your CYA level somewhat depending on how many tablets you use. You cannot use Dichlor for this purpose since it dissolves too readily in the water -- Trichlor is actually better for that "concentration" purpose though you may need to rub it in.

    Keeping the overall pool at shock level and having patience with regular brushing is the best way to get rid of the black algae. The Trichlor method is mostly for the impatient -- the regular brushing with exposure to high chlorine levels is the most important factor.

    Richard

    so on a gunite pool it won't cause too much problems, especially with moving the puck every so often. I have tried to shocking method, I was even pouring the bleach directly over the affected areas (do 4 gals added infront of a return, and then 4 gals over the area). when that didn't work I dropped it down to 1 bottle as normal and 2 bottles over the affected area to keep it at bay.

    I ended up buying 15 tablets off my brother for what came out to $15, so far I have only put in one, and it seems to be doing most of the work, its been in there for 2 days now and only half of it is gone, I keep moving it every hour of so, though it has been moving itself (if someone can explain that).

    the shocking wasn't working because I have bad circulation in that area. I need to figure out the best layout for the jets, the pool builders didn't put return jets on 2 of the 4 sides of the pool...and even more so, they put 3 on one side, and only 1 on another. there is only one around the steps so I aimed the jet that way and now the corner isn't getting circulation. The previous owners didn't use automatic chlorinator but a floater.

    I'm just glad that the black algae is finally going away.
    30,000gal In-ground Gunite Pool DE filter
    Polaris 380 APC

    BBB method all the way - Newb, like to absorb info and chatter, but take the experts' advise

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    Re: Dreaded Black Algae

    Well, I hate to say this, but you don't get rid of black algae that fast.

    Black Algae:


    Perhaps the most aggravating strain of algae, it has been compared to herpes; "once you've got it, it's there for life." This is not entirely accurate, but the difficulty in eradication is due to the strong roots and protective layers over top of the black algae plant. Black algae will appear as dark black or blue/green spots, usually the size of a pencil eraser tip. Their roots extend into the plaster or tile grout, and unless the roots are destroyed completely, a new head will grow back in the same place. The heads also contain protective layers to keep cell destroying chemicals from entering the organism. Like yellow algae, black strains can bloom even in the presence of normal sanitizing levels and proper filtration. I was once told that this form of algae commonly enters a pool inside the swimsuit of a person who's recently been to the ocean.

    Taken from this site:
    http://www.poolcenter.com/algae.htm

    I think the pool people here will tell you the same. That black algae will be alive in your pool for awhile just waiting for a chance to start growing again.
    Hotrod30

    20 X 40 foot vinyl Borates and Salt Pool
    Rolachem Chlorine Feeder
    Hayward 27 inch sand filter with 80 lbs of pea gravel
    Jacuzzi Splash Pak SP55 DE filter in parallel
    Pentair VF3050 pump

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    frustratedpoolmom's Avatar
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    Re: Dreaded Black Algae

    Exactly. Be sure to brush the algae spots daily even several times a day, to break thru the protective layer so the chlorine can get to the insides/roots. Without brushing it will be difficult to get rid of.
    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
    http://www.PerfectlyClearPoolService.com

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