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Thread: Pool turned green overnight - need help identifying cause

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    Pool turned green overnight - need help identifying cause

    Hi all,

    Up until a few days ago, my pool was a clear sparkling oasis. Then yesterday morning, I looked outside and saw that the water had turned green. I walked over to the pool and the water is clear so I can see the bottom just fine, but there is still a light green tint. I emptied out the skimmer basket as I do every morning and there was a dead frog (nothing unusual for us). Then I went to the filter basket by the pool pump and noticed another dead frog in there! I was dumbfounded as to how a frog could have managed to bypass the skimmer basket and crawl/swim/get sucked up to the filter basket, but then I found out that a friend who came over on Sunday for a little get together had emptied the skimmer basket and a frog somehow escaped the skimmer basket. He thought the frog went back into the pool but he couldn't find it anywhere, so now we know how the frog made it up to the filter basket.

    Anyways, my theory is that the frog was in the filter basket for 24-36 hours and my pump/filter essentially was making "frog soup" and the resulting organic material was being passed back into the pool which acted as super fertilizer to spark an algae bloom. Thinking this had to be the case, I poured several gallons of bleach into the pool yesterday, which usually clears up any algae quite quickly. However, this morning, the pool was still greenish in color so I went and got several more gallons of bleach to dump in, which I just did, so I will have to wait to see if that works.

    Something else worth noting is that I have been running the SWG the past 4 or 5 days and it appeared to be working correctly. However, my question is, if the SWG was running correctly, shouldn't the chlorine from the SWG taken care of the algae/green water in the first place? Or would it be possible that my SWG is actually the cause of the green water somehow? The fact that the water is a lightly tinted green and the water is still completely clear to see all the way to the bottom, makes me wonder if somehow copper had something to do with it? But how would copper get into the pool all of a sudden and overnight, when we've never had a copper issue in the past 4 summers?

    I know I need to test my water and post the results here but I was just curious if anyone has any idea what would cause water to go green over night (if it was the frog in the filter basket and/or the SWG or something else)? And if it is a copper issue, how would I go about testing it and how would I resolve it?


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    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: Pool turned green overnight - need help identifying caus

    I don't think the frog had anything to do with it.

    What are your test numbers for chlorine and CYA?
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: Pool turned green overnight - need help identifying caus

    +1 what JohnT said.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Pool turned green overnight - need help identifying caus

    If one frog for 24 hours caused the pool to green every time ... My pool would never be clear with all the dead lizards, mice, birds I find in my pool ... often after much longer than 24 hours to the point they are almost liquified I should probably check more often
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Charlie_R's Avatar
    Join Date
    May 2013
    Mexico, MO

    Re: Pool turned green overnight - need help identifying caus

    Have you ordered your TF-100 yet? link in Duraleigh's sig.

    You won't regret being able to test your own water. Pool stores tests are notoriously inaccurate. I suspect semi on purpose to be able to sell chemicals that you don't need.
    15'x48" 4500 gallon Intex pool, buried 1.5 ft. Pac-Fab Dynamo 3/4 hp pump. Hayward S180T sand filter, bought used. Taylor K-2006 test kit. Rocket mass heater based wood fired pool heater.

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Pool turned green overnight - need help identifying caus

    If it's crystal clear and green, perhaps the pH is out of range and dissolved iron is precipitating out?

    There's really no way to know without test results.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Pool turned green overnight - need help identifying caus

    Thanks everyone for the replies. I thought it was a little unusual that one frog could cause the water to turn green overnight since we've had tons of frogs and random animals before and never had this happen. Since it's likely not the frog, then I don't think it's necessarily an algae issue because I put in a ton of bleach and vacuumed, but the water still looks green... usually when I vacuum up algae, you can see exactly where the vacuum cleaned up the algae... but not this time. I'm thinking it could be a copper issue or some other issue that isn't related to algae. Anyways, I ordered another test kit as you suggested and hopefully it will get here by tomorrow or Friday, so I will keep you all updated.

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