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Thread: Black algae again.. Shock and Polyquat 60?

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    Black algae again.. Shock and Polyquat 60?

    So do to my own fault I let my FC get low and I stopped using a weekly dose of Polyquat 60 for a few weeks and I have a few small spots of black algae again. I have a couple of questions please and I would appreciate your help. I have a plaster pool in FL, I own a wire brush and I've shocked the pool to 50ppm.


    1. Can I use a high dose of Polyquat 60 and shock the pool at the same time.


    2. Why black algae?? I would much prefer green algae but it seems like when I screw up I have this beautiful clear water and black algae. Why?
    15k Diamond Brite, Aquarite SWG, 1.5hp StaRite, Hayward Star Clear 17502, AquaCal heat pump, Pentair Great White pool cleaner

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    Mod Squad jblizzle's Avatar
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    Re: Black algae again.. Shock and Polyquat 60?

    1. Why? Chlorine is what is required to rid the pool of algae and prevent it from coming back. The Polyquat is just a backup to aide in preventing algae if the FC gets too low. You should NOT be needing to add it every week if you are properly maintaining FC levels based on your CYA level

    2. Lucky?

    EDIT: You need to follow the SLAM process, not just add a bunch of FC at once. [slam:16a5l3fx][/slam:16a5l3fx]
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    Re: Black algae again.. Shock and Polyquat 60?

    I have had good luck leaving the FC at normal levels and brushing off the black algae. The black algae is usually just very small spots and I haven't had the need to go through the SLAM process to get rid of it. The main thing about getting rid of black algae is exposing it to the chlorine - if you don't brush it, and I mean BRUSH it (with a WIRE BRUSH), it will stay there. You could SLAM at mustard algae levels, but if you don't brush it open, it's going to stay.

    Can you post pictures of what you have? I'd like to make sure you have black algae before you start anything. For me it tends to get onto the grout around the water line and into any rough surfaces in my plaster (I need to replaster).
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    Re: Black algae again.. Shock and Polyquat 60?

    Here is a photo. Its a minor case of black algae. Random spots here and there but its black algae.
    Attached Images Attached Images
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    Re: Black algae again.. Shock and Polyquat 60?

    SLAM... never heard of it, thank you for the link. I just read about it and it makes sense. Last time this happened I would shock the pool and 24 hours later the chlorine would drop to normal. I couldn't figure out why that was happening but now it makes sense.

    I think I will wait and SLAM the pool after the holidays. The family is going want to use the pool this long weekend. I just checked the pool now, 24 hours later, and its back down to 10 ppm. I'll get my brush and chlorine jugs ready and do it the right way. I'll dose the pool in the morning and the afternoon. Best I can do with my work schedule.

    I take it from your comments the Polyquat is a preventative not a treatment so I will save some money and not use it during the SLAM.

    Thank you again.
    15k Diamond Brite, Aquarite SWG, 1.5hp StaRite, Hayward Star Clear 17502, AquaCal heat pump, Pentair Great White pool cleaner

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    Mod Squad jblizzle's Avatar
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    Re: Black algae again.. Shock and Polyquat 60?

    Sounds like you are on the right track now.

    Do you have a FAS-DPD test kit? Since you appear to have measured a FC of 50ppm, I am guess you do and should be set to SLAM.
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    Re: Black algae again.. Shock and Polyquat 60?

    You are correct, that's black algae.

    Brush it HARD. If you don't see the black things floating around after you brush, you didn't do it hard enough. I can't get it to move with a poly brush. You should probably also see the color of the algae on the pool lighten, it will be a dark green rather than black.

    I can't stress enough, if you don't break that waxy surface on the black algae, you will not kill it.

    For small spots, I use a wire welding brush.

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    Re: Black algae again.. Shock and Polyquat 60?

    Quote Originally Posted by jblizzle
    Sounds like you are on the right track now.

    Do you have a FAS-DPD test kit? Since you appear to have measured a FC of 50ppm, I am guess you do and should be set to SLAM.
    I have the taylor 2006. I use it for more than just the pool. I am on a well water system and I use to measure my FC on a chlorine injection system. No strips here
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    Re: Black algae again.. Shock and Polyquat 60?

    Quote Originally Posted by RobbieH
    You are correct, that's black algae.

    Brush it HARD. If you don't see the black things floating around after you brush, you didn't do it hard enough. I can't get it to move with a poly brush. You should probably also see the color of the algae on the pool lighten, it will be a dark green rather than black.

    I can't stress enough, if you don't break that waxy surface on the black algae, you will not kill it.

    For small spots, I use a wire welding brush.

    I have a full metal stainless brush but these black algae spots are hard to break with the pole and metal brush end. It might sound crazy but I will leave the FC this weekend at normal levels and take a metal brush to these algae spots on a personal level. Thanks for the suggestion.
    15k Diamond Brite, Aquarite SWG, 1.5hp StaRite, Hayward Star Clear 17502, AquaCal heat pump, Pentair Great White pool cleaner

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    Re: Black algae again.. Shock and Polyquat 60?

    Exactly. I have one of those brushes too, and I bent one of my (wimpy) poles trying to use it for black algae. My wife seems to enjoy holding me underwater while I scrub the bottom of the pool... hmmm....
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Re: Black algae again.. Shock and Polyquat 60?

    Bet you have life insurance... ....Wife and Life bad medicine.
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    Re: Black algae again.. Shock and Polyquat 60?

    Quote Originally Posted by whowouldfigga
    1. Can I use a high dose of Polyquat 60 and shock the pool at the same time.
    You don't want to do that because 1) algaecide does not kill algae quickly -- it is better used for maintenance as insurance though it is not really needed if sufficient chlorine levels are maintained and 2) high levels of chlorine break down algaecide so it would be wasteful to do both at the same time.
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    Re: Black algae again.. Shock and Polyquat 60?

    One final question about the FC shock level. I use the Pool calculator and I just want to make sure I should be using the Mustard algae # for shocking black algae
    15k Diamond Brite, Aquarite SWG, 1.5hp StaRite, Hayward Star Clear 17502, AquaCal heat pump, Pentair Great White pool cleaner

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    Mod Squad jblizzle's Avatar
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    Re: Black algae again.. Shock and Polyquat 60?

    Regular shock value and a lot of brushing. Note the Pool School chart is more aggressive.
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    Re: Black algae again.. Shock and Polyquat 60?

    Quote Originally Posted by RobbieH
    Exactly. I have one of those brushes too, and I bent one of my (wimpy) poles trying to use it for black algae. My wife seems to enjoy holding me underwater while I scrub the bottom of the pool... hmmm....
    Thanks! I got a visual!
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