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Thread: Black algae?

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    Black algae?

    I have had a very strange problem the last couple of week. I was going away for a couple of days and put two of the Duration plastic coated capsules in the skimmer to hold the pool while away. When I came back the capsules and the skimmer basket had a black deposit on them. There was also black staining on and around the bottom drain. The next morning the black had started to spread across the liner. I brought the basket to two different pool stores neither had seen anything like it. I brought a bottle of the Black Treat brand bromide based algae cleaner which started clearing thins up right away, but it took 2 weeks of brushing and keep FC high to get it all cleared up. Finding it hard to believe a chlorine tablet could cause such a problem. I decide to experiment using another of the Duration tablets and sure enough in 2 days the black was back on the capsule and skimmer basket (which was a new one). Anyone ever heard of anything like this or have any idea how a chlorine product could cause such a problem?


    - - - Updated - - -

    Oops title should read Black Algae!
    Last edited by Butterfly; 09-06-2014 at 01:20 PM. Reason: fixed title

    17,5000 Gallons
    IG Vinyl
    Cartridge filter

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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Black algae?

    If it's algae, it usually occurs when the FC/CYA ratio gets too low. HTH Duration tabs are Cal-hypo, but perhaps they didn't dissolve quickly enough to maintain an FC that was at least 7.5% of the CYA level at all times. See the Pool School for more info including the Chlorine/CYA Chart.
    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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