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Thread: Black Algae

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    Black Algae

    I am in need of advice. I have a SWG and have black algae mainly in the hot tub. It is a relatively small amount. There is also a small amount on the pool wall. I had my water tested yesterday and here are my results.
    FAC - 0
    TAC -0
    Salt-3100
    CH-200
    CYA-0
    TA-140
    ph - 8
    Acid -5
    I added 27 oz of muratic acid yesterday,brushed, vacummed and back washed. Please advise regarding the best way to proceed to get rid of the algae.
    Thanks
    M Turner
    17,000 gunite, Pentair Triton II sand filter, Whisperflow 2 hp pump

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    frustratedpoolmom's Avatar
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    Re: Black Algae

    Hi, MTurner, Welcome to the forum

    First, if you haven't done so already, check out Pool School... there is a ton of information there that you'll find useful.

    The trick to getting rid of true Black Algae is brushing/scrubbing while your chlorine is up. It's got a tough outer shell that is resistant to chlorine - brushing knocks that shell off so the chlorine can reach the insides. What kind of pool is this?

    But first, was that PH test AFTER you added acid? You need to lower it down to 7.2 ASAP. Have you seen the Pool Calculator (link in my sig)? With high TA of 140, the PH will rise fairly rapidly with an SWG/spa. So you'll need to keep adding acid lowering the PH down to 7.2 everytime. The acid additions will also lower the TA and eventually the TA will get to 70-80 which should be a good level for your pool set up.

    You also should raise your CYA up to the 60-70 level, and you should take care of that today if possible. See Water Balance for SWGs.

    You'll need your own test kit - there is an article in Pool School that tells you all about the two we recommend.

    After you get the PH down to 7.2, you can begin to work on your lack of chlorine/algae issue. Is the SWG producing chlorine?
    How does the water in the pool look (cloudy/clear/green?) Did you just open or install this pool?

    You can put your pool equipment/specs in your signature.... Go to User Control Panel, then Profile, then Edit Signature.

    Hope this helps, post back if you have questions on anything I said.
    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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    Re: Black Algae

    Thanks for the advice. The SWG is working properly. I added the acid after the test (amount recommeded at the store). I am reading and trying to get up to speed as quickly as possible. We have had the pool for 3.5 years. The water is cloudy.
    M Turner
    17,000 gunite, Pentair Triton II sand filter, Whisperflow 2 hp pump

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    Butterfly's Avatar
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    Re: Black Algae

    Hi MTurner,

    I suggest that you leave your SWG off and raise your CYA only to around 30 for now until you are done shocking.

    The higher the CYA level, the higher the shock level and therefore it will take more gallons of bleach/liquid chlorine to reach shock level.
    This translates to $$. Just trying to save you some money during the shock process

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    frustratedpoolmom's Avatar
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    Re: Black Algae

    Quote Originally Posted by Butterfly
    Hi MTurner,

    I suggest that you leave your SWG off and raise your CYA only to around 30 for now until you are done shocking.

    The higher the CYA level, the higher the shock level and therefore it will take more gallons of bleach/liquid chlorine to reach shock level.
    This translates to $$. Just trying to save you some money during the shock process


    Welcome to TFP
    Excellent suggestion! Since the water is cloudy, and the FC 0 you have to shock - it does make sense to keep the CYA level at 30 until things stabilize, then you can increase it later. (Wish I'd thought of that... LOL)

    Read the article "How to shock your pool" in Pool School. (brushing the algae spots while shocking should eliminate them.)
    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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