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Thread: Black and brown spots...could it be algae?

  1. Back To Top    #1

    Join Date
    Aug 2007

    Black and brown spots...could it be algae?

    Hi all,
    I have noticed an increase in black and smudgy brown spots on the sides and bottom of my inground marcite pool. They are less than dime shaped in size. I check my pool levels once a week and everything has been in range. I've tried brushing them with a nylon brush as well as black algaecide to no avail Any ideas or thoughts?
    Thank you!
    Mizzy in Florida

  2. Back To Top    #2
    mbar's Avatar
    Join Date
    Apr 2007
    Ashland PA
    To check if they are organic, use a trichor puck, or some chlorine in a sock and rub on the stain - if it lifts off it is organic. To check if it is mineral (metals), use some crushed up vitamin C tablets in a sock, or some ph down, and rub on stain. If it lifts off it is mineral.
    16x33 fiberglass pool sand filter

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