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Thread: still seem to have algae

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    still seem to have algae

    So I finally got my stabilizer down in the pool, down to about 50, Ph about 7.4, TA about 120. FC about 3-5 using SWG. Problem is, my pool still seems to be growing some algae. I had dumped a lot of bleach in, do I need to dump some more in? I don't know what else to do.
    12000 gal diamond brite pool with 400 gal spillover spa, 1 1/2 HP pump and Hayward 1100 cartridge filter, Hayward Heatpump.

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    JasonLion's Avatar
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    They key to reliably killing off algae is to bring the FC level up to shock level, around 16 for your CYA level, and hold it there by testing the FC level and adding more chlorine several times a day to bring it back up to shock level. Only when the FC level holds overnight are you done. To do this you need to be able to measure FC levels above ten, which requires a good quality test kit. I suggest one from TF Test Kits, see the link in my signature, or the Taylor K-2006 which isn't quite as good a deal but is also fine.
    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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    so even if my regular FC level of 3 or 5 is holding overnight, I still need to shock it?
    12000 gal diamond brite pool with 400 gal spillover spa, 1 1/2 HP pump and Hayward 1100 cartridge filter, Hayward Heatpump.

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    JasonLion's Avatar
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    Yep, some kinds of algae can survive medium chlorine levels. They can't get established when there is chlorine, but once in place they build up a biofilm that protects them from reasonable chlorine levels. It takes high chlorine levels maintained for a few days to get through the biofilm.
    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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    If the algae seems to be clinging to pool surfaces, brushing can help speed up the process of killing it (by providing more surface area and exposing non-slimy areas). Also, is the algae green or is it yellow/mustard in color? If the latter, then this is a heartier algae that requires an even higher chlorine level to kill.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    well I brush and brush, and it just keeps coming back. It looks more blackish than anything else at this point. Given that Florida is very prone to Mustard Algae, I'd guess its probably mustard.
    12000 gal diamond brite pool with 400 gal spillover spa, 1 1/2 HP pump and Hayward 1100 cartridge filter, Hayward Heatpump.

  7. Back To Top    #7
    Use Jason's calculator (in my sig) and shock your pool pronto! Since you suspect mustard, I would shock (with bleach) for mustard. It may also be black algae, which is also quite resistant to normal FC levels.

    Do not stop shocking until these criteria are met:

    1. FC holds overnight (test FC at dusk, and again at dawn. If the numbers are within 0.5, you are good)
    2. CC is 0 (max 0.5)
    (3. the water sparkles)

    Keep brushing your pool and backwashing (or whatever) your filter as necessary.

    8000 gallon 20' x 48" round vinyl frame pool, 12" sand filter (don't have the specs on the pump), TF100 test kit
    Handy Links: PoolMath, TF-100 Test Kit, Pool School, CYA-Chlorine Chart
    "Shock" is a process, not a product!

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    With a CYA level of 50 ppm, the yellow/mustard algae shock level is almost 30 ppm FC. Though this sounds very high, it is technically equivalent to having an FC of 1.4 ppm with no CYA. Before you raise the FC that high, lower your pH down to 7.2 first -- that will make the higher FC level more effective since the bleach or chlorinating liquid will make the pH go up until the chlorine gets used up. You might have to roughly guestimate with the pH test since the already high chlorine level may make that test hard to read.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

  9. Back To Top    #9

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    I am happy to reply, the algae appears gone, pool is nice and clear. I used lots of chlorine for a few days and that appears to have done it.
    12000 gal diamond brite pool with 400 gal spillover spa, 1 1/2 HP pump and Hayward 1100 cartridge filter, Hayward Heatpump.

  10. Back To Top    #10
    JasonLion's Avatar
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    Congratulations!
    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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