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Thread: Black algae??

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    lka674's Avatar
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    Jul 2012
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    Black algae??

    Hello,

    I believe I have 2 small spots of black algae growing in my spa...started with one spot in the corner that was fairly small, but now it's a little bigger and there is a new spot near it up on the wall.

    Our spa spills into the pool and the water recycles between the pool and the spa.....we do not keep the spa heated so it stays at the same temp as the pool year round as it only takes about 10 min to heat it up when we want to use it and that's not very often to be honest. My test #'s are perfect for where I want to keep them...considering I'm running a slightly neg CSI to place a band aid on my high CH level....I'm passing OCLT's with ease....but the spots remain and won't brush off. The water in both pool and spa is crystal clear and there are zero signs of any algae in the pool itself or any of the tile or coping.

    Do you think I'm right about it being black algae? And if so, does that mean I have to start the shocking process for the entire pool????? How I dread having to do that!! I just recently got everything in check for hitting my target CSI.

    Today's numbers:

    FC - 8
    CC - 0.5
    TC - 8.5
    pH - 7.4
    TA - 70 (we run lots of water features frequently)
    CYA - 60 (we have 100% direct sun exp all day)
    CH - 550

    Any advice is appreciated!
    Pool grand opening Sept 2010. 100% sun exposure. Beach entry with fountain, IG gunite pool, approx 11,000g. Hayward HK sand filter. Intelliflow VS 350 pump w/ max flow rate 160 gpm. Dolphin (cordless) M5 Liberty pool cleaner. The pool has waterfall at one end with a tanning ledge and a spa at the other end that has a spillway into the pool and there is a water shear falling from the pool equip wall into the spa. DH did a beautiful job of designing it himself!

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    Mod Squad Bama Rambler's Avatar
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    Re: Black algae??

    Can you scrape it off?
    If you can't it's not algae and it's most likely a stain.
    If you can, wipe it on a piece of white paper and if it's green looking, it's black algae.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    lka674's Avatar
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    Re: Black algae??

    Hi...sorry! We've had some stuff going on with fam and then had to take off out of town, so I apologize for posting and then not getting back to you once you had commented!

    The DH WAS able to grind it off with a pool pumice tool and he actually went down there with a mask and snorkle to get a really good look and he now swears it really looked more rust like than black once you were up close and personal.

    So....no more black dots...and so far none reforming. I think you were correct about it being a stain!

    Thanks so much for the comments and suggestions. I appreciate it!
    Laura
    Pool grand opening Sept 2010. 100% sun exposure. Beach entry with fountain, IG gunite pool, approx 11,000g. Hayward HK sand filter. Intelliflow VS 350 pump w/ max flow rate 160 gpm. Dolphin (cordless) M5 Liberty pool cleaner. The pool has waterfall at one end with a tanning ledge and a spa at the other end that has a spillway into the pool and there is a water shear falling from the pool equip wall into the spa. DH did a beautiful job of designing it himself!

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    Mod Squad Bama Rambler's Avatar
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    Re: Black algae??

    Glad you got it removed and glad it wasn't algae, though stains are their own sort of evil.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Black algae??

    A friend found rust spots in their pool after the lawn service used fertilizer containing iron.
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

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    lka674's Avatar
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    Re: Black algae??

    Oh yes....very familiar with those stains...DH got some on our tanning ledge. STILL working to get those off and it's been about 8 months!
    Pool grand opening Sept 2010. 100% sun exposure. Beach entry with fountain, IG gunite pool, approx 11,000g. Hayward HK sand filter. Intelliflow VS 350 pump w/ max flow rate 160 gpm. Dolphin (cordless) M5 Liberty pool cleaner. The pool has waterfall at one end with a tanning ledge and a spa at the other end that has a spillway into the pool and there is a water shear falling from the pool equip wall into the spa. DH did a beautiful job of designing it himself!

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    Butterfly's Avatar
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    Re: Black algae??

    The DH WAS able to grind it off with a pool pumice tool and he actually went down there with a mask and snorkle to get a really good look and he now swears it really looked more rust like than black once you were up close and personal.
    If you have a small amount of metal stains (rust, iron, etc) you can crush some cheap vitamin C tablets (ascorbic acid) in a sock. Then hold the sock on the stain for a few minutes. If the stains are metal, they should fade or disappear.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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