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Thread: Another Black algae

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    Another Black algae

    New member, been reading through old black algae threads. My pool is in Florida and receives moderate sunlight throughout the day and is never covered. Last year I had black algae start in the more shady areas of the pool. I've noticed there are more spots where the plaster finish is more worn. Refinishing the plaster and draining the pool are out of the question. Refinishing costs too much and draining a pool in florida usually means it will pop up due to the low water table. Last year I went through a regiment of Leslies black algae killer, but it literally did nothing. I even got in the pool with a scuba tank and wire brush, hitting every area I could find. I found if I leave a trichlor tab on the spots over night it will disappear, but even the ones I killed last year are back. This year as summer comes ive decided Im going to defeat it, but now its spread more and there are probly hundreds of spots, beyond hitting them with a tab. I dont know why, but I bought another half gallon of black algae killer after being told once I add enough they should brush off..........I'm a sucker, but after brushing my pool for the fourth time today and having no effect on the spots I feel like Im going to get no results. I need some more options.

    Current readings
    FC 3
    CH 230
    CYA 99
    TA 120
    PH 7.6
    TDs 500
    PHOS 600
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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    Richard320's Avatar
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    Re: Another Black algae

    Sounds like a job for Pool School.
    1) Those readings look like they came from the pool store. Get your own test kit. Odds are they won't have the one you need in stock at Leslies. The DPD test kit is not the same as FAS-DPD.
    2) If, by some stretch, those readings are correct, your FC is too low for your CYA level. But they probably aren't correct, which is why you need your own test kit.
    3) The defeating algae article in Pool School is a good place to start - but you'll be brushing with the wire brush far more than normal to remove the biofilm (think scab) the algae forms.
    4) If you maintain FC above target for your CYA level all summer, I suspect you will be rid of it for good. The visible spots in a week or so, the hidden stuff will take a while.

    But first, get some readings, replace enough water to lower the CYA level to something manageable for the shock process - and you'll need accurate readings, so don't start before you get the test kit, because you may need to do several partial drains - and commence the shock process. Study Pool School while you wait. If you order the kit from http://tftestkits.net/ tonight, you'll probably have it Monday or Tuesday.
    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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    linen's Avatar
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    Re: Another Black algae

    Welcome to tfp, sweedish15

    Richard320, gave you great advice!

    Are you certain it is black algae? Usually black algae is slimy and when smeared is dark green on the inside. Have you done that test?
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

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    Re: Another Black algae

    yep thats exactly what it is. They are not really black, if you smear them w your finger its a real dark green spot. Found some growing on the water fall in the cracks of the rocks which is where I suspect it started. As leslies said, I did another 24oz of black algae killer which has again done nothing after brushing the pool 3 times today.........shocking right.

    As you all suggested I ordered a set of decent test kits, I went with the taylor k-2006 set. It will be here next week. As said by the first reply those test results were from leslies. Just like everything else in life if you want something done right you have to do it yourself. I dont thnk they test very accurately as leslies and its dependant on the employee you get. I was told my phosphats were at 200 last week and added half a bottle of their phos free and a week later they told me my phoshates went to nearly 600 without any debris leaves swimmers etc in the pool all week.

    From reading pool school it appears i need to keep my FC much higher than in the past. But first i would like to get my own accurate CYA reading.

    For future reference, do you all keep your free chloride up by literally adding liquid chlorine everyday? I feel like it will take alot of liquid chlorine to keep it up near 8-10.
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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    Richard320's Avatar
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    Re: Another Black algae

    Quote Originally Posted by sweedish15

    For future reference, do you all keep your free chloride up by literally adding liquid chlorine everyday? I feel like it will take a lot of liquid chlorine to keep it up near 8-10.
    Yes.

    I started out with a pool with CYA about 220-240. So I had to keep FC up at around 20. Which meant I could only use the FAS-DPD test for Chlorine. The good news is, the usage isn't really any greater than if CYA is down around 50. There's a lot to add initially to get it up there, but after that it was about 2 ppm/day, which on my pool works out to about a qt of 12% per day.

    But at this point, it's all speculation because your test results are doubtful.
    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: Another Black algae

    To update, I got my Taylor k-2006 test kit today and these were my results as of early this evening.

    FC-0
    ph-7.4
    TA-115
    CA-335
    CYA between 90-100

    According to the pool calculator and reading the charts in pool school with my CYA that high I needed a FC level of 39 to bring it to shock level. So using the pool calculator I added the necessary 5 gallongs of 12% liquid chlorine which should bring me right to 40 FC. I gave the pool a good brushing and Ill test again later tonight. I really dont want to drain 50% of my pool as according to the calculator to bring down my CYA to 50. Im on city water and its expensive. After this shock I will just maintain the higher level of FC for a while until more water splashes out. Black spots are unchanged, dont waste your money on leslies black algae killer, since the beginning of this thread I've done 4 treatments and brushed the pool at least 10 times during the treatments and it hasnt helped. I had another pool owner come by and he confirmed its black algae for sure, so Im not crazy.

    Wish me luck
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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    Re: Another Black algae

    been about an hour since the chlorine addition:

    FC-40 (shock level) right on
    CC-3

    What should i do to get the combined chlorine down? Or does that come down as the bad stuff comes out of the water, meaning maintain shock level until the cc goes to .5 or lower?
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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    Richard320's Avatar
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    Re: Another Black algae

    Quote Originally Posted by sweedish15
    been about an hour since the chlorine addition:

    FC-40 (shock level) right on
    CC-3

    What should i do to get the combined chlorine down? Or does that come down as the bad stuff comes out of the water, meaning maintain shock level until the cc goes to .5 or lower?
    Open a can of POP. Pool Owner Patience. Just keep FC up there and it will clear up.
    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: Another Black algae

    I chose corona, then when brushing a spot i realized the bristles on my wire brush are so spread apart they were not smashing the outer layer of the black algae spots. Against better judgement I strapped on a dive tank got a nice thick wire brush and went to town on the spots for about an hours. Showered real well after getting out of the chlorine, but suprisingly the chlorine didnt bother me much.

    While diving I found out there is a ledge under my water fall that had huge chunks of black algae that I never knew existed. scraped them good and vacuumed the entire pool. I think this will be the break through I've been looking for.
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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    linen's Avatar
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    Re: Another Black algae

    How soon can you get that cya down...I would make that a priority.

    Quote Originally Posted by sweedish15
    Against better judgement I strapped on a dive tank got a nice thick wire brush and went to town on the spots for about an hours. Showered real well after getting out of the chlorine, but suprisingly the chlorine didnt bother me much.
    Not surprising, the amount of active chlorine is really not that high at your higher cya level, though sometimes the higher CC level you have can bother. Our guideline is you can swim up to your shock level for your cya, so you were not too far off.
    TFP Expert who uses Pool School and my TF100 test kit along with PoolMath for my: Round 11K gallon AGP with deep end, 20" sand filter, Matrix 1hp 2spd, 6 2ftX20ft solar panels (and solar cover!), Intex SWCG (copper bars disconnected) and a Rubadub hot tub (chlorine). The SLAM process is not finished until: 1. CC < 0.5 ppm, 2. An OCLT < 1.0 ppm and, 3. The water is crystal clear.

  11. Back To Top    #11

    Re: Another Black algae

    Well over night and throughout the morning the pool has gotten a steady 12 hrs of moderate rain

    FC went from 40 to 31
    CC stayed at 3

    Theres literally no sun out right now so I added the 1 gallon 2 cups per the pool calculator to bring the FC back up to 40
    15,500 gal, IG plaster, cartridge pentair cc100, pump pinnacle single speed 1hp, built 1981 (mine for 4 yrs), standard chlorine.

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