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Thread: Black algae question

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    Black algae question

    Okay, im at my wits end with this black algae in my pool. I have kept the pool at shock level or very close by for a week now. (there are some times it slipped below recommended shock level but not for more than a couple of hours) Anyways my black algae has developed a force field. I have been brushing rigourously for a week now with a metal brush, but it wasn't doing jack. The outer layer of algae has turned gray and calcified of sorts. A metal brush does nothing to this outer shield. After a week, I finally got tired of brushing and moved up the arsenal to a pumice stone. The stone seems to be able to break up that outer layer and expose fresh dark green algae, but it is certainly a workout. Is there an easier way? Or do I continue on with the pumice stone and just curse my bad luck? Im currently adding about 2 gallons of 10% clorine a day to keep it at that FC level. The pool is crystal clear except for were these black algae spots are. I do confess that the black algae has been growing for about 6 months now, and Im finally trying to nuke it.

    FC is 25 right now
    CC is .5
    CYA is 40
    ph is 7.5
    16k, DE, IG, Plaster

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    JasonLion's Avatar
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    Re: Black algae question

    Black algae is very very difficult to get rid of. If you only have a few isolated patches, try rubbing it with a trichlor tablet for a while. With black algae, maintaining shock level isn't the most crucial thing, it is removing layer after layer of protective crust to get at the algae underneath.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Black algae question

    It would be helpful to purchase a stainless steel brush for the algae if you don't already have one. BA is super tough!

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    Re: Black algae question

    Quote Originally Posted by JasonLion
    Black algae is very very difficult to get rid of. If you only have a few isolated patches, try rubbing it with a trichlor tablet for a while. With black algae, maintaining shock level isn't the most crucial thing, it is removing layer after layer of protective crust to get at the algae underneath.
    The pool is 99% clean just some black algae inbetween tiles and some spots on the wall. Should I lower the level of FC to normal and just attack the algae with a triclor puck?
    16k, DE, IG, Plaster

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    JasonLion's Avatar
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    Re: Black algae question

    If you are trying the trichlor approach, keep FC at the high end of the normal range to prevent it from spreading, but no need to stay all the way up at shock level.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Black algae question

    Okay thanks! Ill let it come down a bit and attack it with pucks on a stick.
    16k, DE, IG, Plaster

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    Aquatica's Avatar
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    Re: Black algae question

    best way to get rid of black algae is to drain pool and acid wash it off the surface. hopefully the roots havent got that deep otherwise you will have to chip it out. My father managed a timeshare and they had black algae go down to the rebar! major work. drain the pool and acid wash it before it gets out of control. donnt waste your time with trichlor. I had a pool with black algae on the surface and the only way I got rid of it was to drain the pool and acid wash it. make sure you get rid of it all..so it doesn't come back.

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    Mod Squad zea3's Avatar
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    Re: Black algae question

    Mags, please do not attempt an acid wash at this time! Frequent brushing with a stainless steel brush and keeping FC at the top of the recommended range should take care of the algae problem. You will need to be diligent until all the algae is gone, and you will need to maintain the FC at the top of the recommended range to prevent it from coming back.
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    Re: Black algae question

    I have had more successes than losses in dealing with BA. Get a wire brush and scrub it out as best you can - all of it. This is the hardest part.

    I then superchlorinate to MA levels - and keep it there for a few days... and then always keep/sustain chlorine in the pool. That which doesn't die right away, will go away slowly. Note, the older the plaster (or more specifically, the condition of the older plaster), the harder it will be to kill/control.

    Here's some pictures from a BA job yesterday:






    I have had the FC around 30 for the last 24 hours (CYA~40-50), and - after brushing as much away as I could yesterday, most of it is dead/white-ish-beige this morning. I should have taken a picture when I was there this morning - it looks like a different pool. Will take some (And post) next time I am there. This was new-ish 3MCQ plaster, that had a LOT of dings in it from the Ray-vac. Most of the plaster was good, but BA was in every niche and ding.

    Now I'll also contrast this to another customer (no pictures) with 15 year old plaster - popped holes all over the plaster - where we didn't scrub, but kept ~3<FC<7 for a month... at the end of 30-days it was almost all gone (she didn't want to pay me to jump in and scrub, promised me her kids would do it, and they didn't), and it was hard to find any without looking by the end of the summer.

    It is a battle that can be won. It's not cheap, and it's not easy (my shoulders and sides are KILLING me from intense scrubbing for 4 hours yesterday).

    - Jeff
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
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    Re: Black algae question

    Yikes! That is absolutely awful. Well, even with the elevated chlorine levels, it is really the elbow grease of frequent brushing that makes the big difference in continuing to expose the black algae to the elevated chlorine levels. This is because the living black algae that is deeper in the plaster continues to excrete waxy substances to the surface that inhibit chlorine getting to it to kill it. As painful as it may be, going back the next day or two and brushing again would probably make it go away even faster.
    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
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    Re: Black algae question

    Quote Originally Posted by zea3
    Mags, please do not attempt an acid wash at this time! Frequent brushing with a stainless steel brush and keeping FC at the top of the recommended range should take care of the algae problem. You will need to be diligent until all the algae is gone, and you will need to maintain the FC at the top of the recommended range to prevent it from coming back.

    Don't worry, I'm not that **** motivated! My pool is not nearly as bad as shown in the pics above. I spent an hour tonight scrubbing inside the pool. There in no "green" algae left, just crusty gray left. A few spots show green after scrubbing but not many. I think after a week of swimming/scrubbing I'll have this puppy licked. Thanks for all the help, I really appreciate it.
    16k, DE, IG, Plaster

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    Re: Black algae question

    Here is the "after" picture, after scrubbing with a 4" steel brush, and three days of FC in the ~30ppm range:





    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

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    Re: Black algae question

    Looks great. Here is the finished product over at my place.





    Thanks for all the help, I really appreciate it!
    16k, DE, IG, Plaster

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    Re: Black algae question

    Sure am glad I found this thread. I am in the early stages of curing a BA problem. Too bad I wasted so much time asking the local pool shop for solutions. I have however confirmed that commercial algae removal products do not work. I just bought several cases of liquid chlorine and will shock and scrub til it's gone.

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