Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 13 of 13

Thread: 12" diameter black algae stains

  1. Back To Top    #1

    12" diameter black algae stains

    I'm new here and hopefully my picture is attached. The stains have been there for years. The stain on top of picture with white circle is where chlorine tab was. The stain on bottom of picture is where I used dry acid in a sock. Can black algae get this big? Thanks.
    Attached Images Attached Images
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

  2. Back To Top    #2
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: 12" diameter black algae stains

    Hi Randy, very, very odd stains...
    In the stain at the bottom of the pic, it looks like some fading of the stain has taken place - you are saying you held dry acid in a sock there?
    I can't tell the area you are referring to when you discuss a chlorine tablet? I see three other large black circles...
    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

  3. Back To Top    #3
    Guest

    Re: 12" diameter black algae stains

    Yes, it appears to be black algae. I have seen it get that big before.

  4. Back To Top    #4

    Re: 12" diameter black algae stains

    Yes. About 6 months ago I used the dry acid. The white spot at the top of the stain at the top of the picture is where a 3" tablet was.
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

  5. Back To Top    #5
    frustratedpoolmom's Avatar
    Join Date
    May 2007
    Location
    SWSuburban Chicago, IL
    Posts
    11,965

    Re: 12" diameter black algae stains

    Well, then yeah, I'd concur with Bruce that it's the dreaded BA. Is it anywhere other than these 4 circles? If not, I'd spot treat with chlorine tablets.

    If the BA is living, you need to brush with a SS brush to knock the heads off so the chlorine can attack the insides. BA has a chlorine resistant outer shell - brushing is the key here.
    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

  6. Back To Top    #6

    Re: 12" diameter black algae stains

    There are a few more lighter spots. Thanks for your help.
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

  7. Back To Top    #7

    Re: 12" diameter black algae stains

    I've added 2 close-up pictures to hopefully verify its black algae. Also went to pool store for water test.
    FC-5+
    TA-200
    CYA-100+
    Ph-7.8
    CH-500+
    30,000 gal.

    I added qt of acid and 30 oz genesis shock since test.
    Cruised the site here and realized I'm makings things worse. I've turned off the auto feeder of tablets. Until I get a chance to do a partial drain should I add liquid chlorine or bleach if this is algae?
    Debating on buying FAS-DPD today or ordering TF100 and waiting for delivery. Located in Southern California.

    Please advise on anything and everything. Thanks
    Attached Images Attached Images
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

  8. Back To Top    #8
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: 12" diameter black algae stains

    Your first step is to get CYA down to something reasonable, I would aim for CYA around 40 to 50. That means either a lot of water replacement or an RO treatment.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  9. Back To Top    #9
    Guest

    Re: 12" diameter black algae stains

    How far south in Southern California are you? If you are close by, I would be happy to come and look at it for you. You can PM me if you don't want your location public!

  10. Back To Top    #10

    Re: 12" diameter black algae stains

    You know to me, that looks like an organic stain - like someone had a pile of leaves or, as in the last pool I cleared, immature dates by the 1000s or something that's just sat there. Regardless, like everyone else says, get your CYA down, then your CL up. I find that both organic stains and black algae will fade rather quickly if you maintain FC about 2-3 x MinFC level for several days in a row.
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

  11. Back To Top    #11

    Re: 12" diameter black algae stains

    I have drained half my pool and refilling now. Ordered test kit, should be here next week. Tried to scrape or smear the spots. Nothing. Tried vitamin c tablet. No change. Rubbed 3" puck on it; maybe dulled it a little. Ordered test kit, should be here next week. Then I'm sure I'll have more questions. Thanks everyone for all your help.
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

  12. Back To Top    #12
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: 12" diameter black algae stains

    One trick that often works on black algae on the bottom of the pool is to get some powdered trichlor, brush vigorously with a stainless steel brush and then put a layer of trichlor powder directly on the black algae. If you do this too much it can damage the pool surface, but if done correctly and with a little luck it can take care of things in one application. If you do try this, treat a small area first and see how it goes before tackling the rest of the spots.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  13. Back To Top    #13

    Re: 12" diameter black algae stains

    I received my new test kit. Even after draining about half the pool;
    FC-14
    CC-0
    TC-14
    pH-7.5
    T/A-240
    CH-860
    CYA-100+
    Tested CH assuming copper in water from black algae killer 2 weeks ago(which didn't even touch it)
    I'm assuming I'll have to drain half the pool again? (After my water bill cycles a month)
    Any help is appreciated. Thanks
    15,000 Plaster IG Pool
    AquaRite SWG, C1750 Catridge filter
    G3 Vaccum, T-100 Kit

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •