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Thread: Black Algae around pool lights. Did I treat it correctly?

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    Join Date
    Jul 2014
    Philadelphia. PA

    Black Algae around pool lights. Did I treat it correctly?

    I noticed some black algae starting to grow around my pool lights. They are fiber optic lights and I believe they are cemented into the pool wall. If not, I'm not sure how to remove them. There is a slight crevasse around the light where it meets the wall and that is where the algae is forming. The water is crystal clear. I scrubbed the lights with a chlorine puck, then scrubbed around the light with a toothbrush to remove the algae. After the bits stopped coming off I scrubbed again with the puck. The cleaner is running to sweep up the broken off bits of algae. Is there anything else I should do? Are the little bits that floated to the bottom of the pool now at risk of growing and spreading to the plaster? My chlorine is high right now at 8.5 and my CYA is less than 30. (my pool is almost completely shaded and I have had no problems with chlorine loss, hence the low cya). Thanks!

    FC 8.5
    CC 0
    Ph 7.4
    TA 70
    CH 280
    CYA <30
    water temp 83
    40,000 gallons (estimate), 23 yrs old, IG, plaster, StaRite 3 cartridge filter, Magnetek 2 hp pump, Intellichlor SWG, spa w/ waterfall, pressure side cleaner w/ booster pump, Max-E-Therm Heater

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

    Re: Black Algae around pool lights. Did I treat it correctly?

    With visible algae, you should follow the ShockLevelAndMAINTAIN Process and currently your FC may be too low for that process depending on your actual CYA level. I would certainly suggest you raise the CYA to something that you can at least measure. Your SWG would not have to work as hard if you raised it a bit.

    For black algae you have to brush/scrub them to remove their protection, which it sounds like you did.
    Jason, TFP Moderator
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