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Subject: Algicides


From: Hilda Abreu Utermohlen <hilda>
Date: Friday, August 17, 2001
Ioanna Tsamasfyrou <martsam15 [at] hotmail__com> writes

>I would like to know if anyone has heard of "Algicid", which is a
>biocide used in stones. I am searching for its chemical substance.

"Algicides" are chemicals used for killing algae in swimming pools
and spas (different from "algistats", which inhibit their growth),
when regular pool maintenance activities fail to prevent their
growth. The Pool Maintenance Manual (by Terry Tamminen, McGraw-Hill,
1995) talks about algae and its elimination in its chapter on water
chemistry. The following information is summarized from it:

    There are countless companies producing countless products
    designed to prevent and/or kill algae in pools, spas, or water
    features. Algicides are regulated by the U.S. Department of
    Agriculture as pesticides (they mention it is a felony to use
    these products for purposes other than intended, so anyone using
    algicides may want to check on its regulations). There are
    various types of algicides:

        Copper sulfate (liquid copper, bluestone). Very effective on
        all types of algae. Recommended for decorative ponds or
        dark-colored pools, because of blue-green staining problems.
        It destroys the algae's ability to breath and consume food,
        killing it in the process. It coats the pool surfaces
        leaving a long-term effect. Modern products contain
        chelating agents to prevent this staining, but the staining
        may return in the presence of strong oxidizers, like

        Colloidal (suspended) silver (Silver Algaedyne). Effective
        against all types of algae.

        Polymers. Effective on all types of algae to some degree,
        best on yellow and green algae. Positively charged, they are
        attracted to the negatively-charged algae (as well as dirt).

        Quaternary ammonium compounds (quats). Work like polymers,
        not as effective, will foam if agitated in water. Good on
        green algae. Popular choice in the swimming pool industry in
        some areas.

        Chlorine boosters. One is anhydrous (or aqua) ammonia. Used
        against stubborn yellow or large green algae. Improves the
        effect of chlorine.

        Miscellaneous products. One is Symazine, a polymer; also
        hastens decomposition of chlorine. Electronic devices, not
        as effective.

Hope this works

Hilda Abreu Utermohlen
Conservation Consultant
Centro Cultural Eduardo Leon Jimenes
Dominican Republic

                  Conservation DistList Instance 15:18
                  Distributed: Friday, August 17, 2001
                       Message Id: cdl-15-18-002
Received on Friday, 17 August, 2001

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