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Thread: Invisible Algae?

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    jmills's Avatar
    Join Date
    Jul 2007
    Billerica MA

    Invisible Algae?

    It's been a while since I have written here and I really thought I had mostly BBB down. It seems that I am just catching things before they got really bad. Through the fun and games so far the CYA is 40, Alkalinity 100, hardness around 80, and PH around 7.4.

    When I vacuumed the pool Sunday, after skipping a week, I noticed two small green spots that might have been algae. I first added a full dose of Polyquat. I reread the guidelines on FC levels and realized that I had been running on the low side. My around 7:00 PM CF levels have been in the 2.5 to 3 range. I usually added about 14 oz of 6% bleach according to the Pool Calculator to supposedly bring the level to 4.

    Sunday I realized that I should not have been letting the level get lower than 3. Since the FC was at 2.5 I added 10 oz to get past FC 3 and another 14 oz which is what the pool was using almost every day.

    Monday at 8:00 PM I got the surprise that my FC was 1.5 even though I had put more bleach in than usual. I have read enough here to realize that I probably had stuff growing in the water even though it is crystal clear. It was time to hit it hard. I added 132 oz of 6% bleach hoping to get to a FC of 16.

    Tuesday at 10:40 AM I tested FC at 9. I should mention that I got this number using a one year old Taylor/Leslie's DPD test key. To measure the higher numbers I am using the shot glass method diluting my pool water by 1:1 or 2:1 with distilled water as appropriate.

    Tuesday at 3:15 PM I measured FC at 12. below the Shock level of 15 the pool calculator recommends. I was using this as a project to teach my 10 YO son problem solving and he noticed that the Mustard Algae shock level is 24. He said we should shoot for that. I don't really know how to tell mustard from other algae, so I went along with it. I added 109 oz of 6% bleach. This should have brought FC to 24.

    AM I going too far with the bleach? With my current tools I don't think I can test with any confidence past 15. I have probably rendered the pool unswimmable past the coming weekend.

    Regards, John Luke
    12' x 20' Intex Oval Frame Pool, AG
    Waterway 1 hp TWM Cartridge Filter
    4' x 20' solar panel
    41' water depth
    4393 Gallons according to the box.

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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Invisible Algae?

    Mustard algae shock levels after just seeing a few spots does sound like over doing it.

    With CYA at 40, the FC level will come down pretty quickly, probably two days to get back to normal levels (assuming the algae is all dead at this point).
    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

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