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Thread: Using Algaecide to Treat an Algae Bloom

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    Using Algaecide to Treat an Algae Bloom

    Post split off from this topic by Moderator

    If your CYA isn't too high, hit it with a few pounds of 60%+ granular trichlor, otherwise liquid chlorine. Though I used to absolutely gear away from all copper algaecides (except for last resorts) and will probably get **** from everyone for recommending it...well, it'll probably knock it right out! I'd follow up the super chlorination with a copper or silver-based algaecide, run the pump overnight, and re-chlorinate the heck out of it the next day, because the FC will get eaten up. You might want to follow up with a monopersulfate afterwards to clear up any remaining cloudiness from dead algae and CC. Once everything is trapped in the filter, clean it! Clean it good. This process is what I do in severe mustard algae cases, and works EVERY time. Don't get into a habit of relying on the stuff, though.
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    frustratedpoolmom's Avatar
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    Re: Using Algaecide to Treat an Algae Bloom

    Algaecide is more effective as a preventative than a "treatment" - even then we only recommend the use of Polyquat 60, and only in a few specific circumstances. Here at TFP we routinely discourage the use of copper-based algaecides.

    Your recommendation would put the pool owner thru unneccessary expense and could make the situation worse.

    Chlorine, liquid chlorine, is what is prescribed. There is no reason to advocate the added expense of granular trichlor, and there is no reason to recommend MPS (which is really more suited for indoor pools and spas anyway).

    Once the chlorine kills the algae, the filter can filter it out without the aid of additional products (or in the case of a sand filter, perhaps a little DE in the sand).

    Chlorine, one of the recommended test kits, and POP is what they need to treat an algae bloom.
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    JasonLion's Avatar
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    Re: Using Algaecide to Treat an Algae Bloom

    Granular trichlor is particularly in-appropriate. Trichlors big feature is that it dissolves slowly, which is exactly what you don't want when shocking. It is possible to pre-dissolve trichlor, but it is extra work and many people skip that step. If you forget to pre-dissolve it you end up with damage to the pool surface as the trichlor lowers the PH and raises the FC level right next to the pool surface as it dissolves. Add in that trichlor raises the CYA level, which means you need to use even more chlorine the next time and trichlor is the worst possible choice, of the available chlorine sources.

    Copper and silver based algaecides can both lead to nasty stains that can be expensive to remove, if they can be removed at all. While either one can help kill algae, the risk of problems more than rules out their use for anyone who is hoping to have a trouble free pool.
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    Re: Using Algaecide to Treat an Algae Bloom

    Some comments:

    Quote Originally Posted by dudeguy37
    Post split off from this topic by Moderator

    If your CYA isn't too high, hit it with a few pounds of 60%+ granular trichlor
    Too slow dissolving. Only useful for black spot algae
    , otherwise liquid chlorine. Though I used to absolutely gear away from all copper algaecides (except for last resorts) and will probably get **** from everyone for recommending it...well, it'll probably knock it right out!
    Actually, this is true. Copper (and also silver)) is the only thing that will kill an active algae bloom besides halogens (chlorine or bromine). However, the drawbacks FAR outweigh the benefits, IMHO.
    I'd follow up the super chlorination with a copper or silver-based algaecide, run the pump overnight, and re-chlorinate the heck out of it the next day, because the FC will get eaten up.
    You can do exactly this same procedure of shock, Polyquat 60, and shock again with very effective results and non of the side effects of copper. The polyquat 60 will also acutally help the filter remove the resulting cloudiness since it has some 'clarifier' properties.

    You might want to follow up with a monopersulfate afterwards to clear up any remaining cloudiness from dead algae and CC.
    Why bother with the MPS at all. Unless you use special testing procedures it will test as CC so it actually complicates knowing if you have CC left or not. If you just shock with unstabilized chlorine and there is CC just shock again! (MPS is more useful in indoor pools, IMHO)
    Once everything is trapped in the filter, clean it! Clean it good.
    I agree!
    This process is what I do in severe mustard algae cases, and works EVERY time. Don't get into a habit of relying on the stuff, though.
    If the pool is plaster or fiberglass I just 'nuke' it with very high FC levels, for example, a pool with 30-50 ppm CYA gets shocked to about 30+ ppm FC. The algae dies!
    For a vinyl pool I use the shock, polyquat60, shock method and would shock to about 20 ppm. (However, sometimes the first shock takes care of the problem.)
    Works for green and mustard. Black spot and the cyanobacters and biofilms ("red algae", pink slime, white water mold) need different procedures.

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