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GARGAS: Water and the Aquarium                Page 5

        were only a few products that were used for aquarium fish as additives. There were
        really no problems; the fish grew and reproduced along with the plants. Look at what the
        hobbyist is “bombarded’ with now just about everything under the sun. It appears the
        days of Research and Development in the Tropical Fish Industry have come to an end.
        If someone comes up with an idea for a product, it does not matter if the product works
        but “is it marketable”. Tropical fish have always been my passion and I’ve truly missed
        being involved in breeding as well as developing new products for the hobby.  I’ve
        decided to get back into the breeding of low conductivity soft water species of fish which
        I was doing for all of those who remember me back in the Chicago area before I was moved.
               This is the first article I have written in over 12 years I will attempt to
        answer the questions that many aquarist have when adding additives, or when distributors
        add additives before they ship their fish, especially salt and other so called
        “conditioners” that have a high chloride and sodium content. First, I would like to begin
        with Total Dissolved Solids (TDS) which is the most important water quality parameter
        (not pH) in keeping tropical fish. By the way I am sorry for the math involved here but
        there really is no other way to help you understand TDS.

               First of all we must understand TDS (Total Dissolved Solids). This is a
        gravimetric test which means it is a measurement of weight.  A meter measures the
        conductivity, not TDS. From what I can remember cities like the Chicago, Illinois would
        do this once a year. They would use a group of specific sized ml. beakers;  and weigh each
        one to get the tare weight ( empty weight). The first round  measured a non-filterable water
        sample, raw water from the plant that was taken from a few miles off shore. The beakers
        would be heated slowly to evaporate the water, and then they would then be cooled. Each
        beaker would then be weighed and the result would be multiplied by a known factor
        (I think it was a 1000). This would be non-filterable TDS. The totals would be averaged
        together to get a TDS amount in mg/l or ppm. They would do this again but filter the raw
                                                 photo: MFJacobs...2003
        water sample through a micron filter.  The result would be filterable TDS. Usually a
        water report would will have 2 TDS measurements; filterable and non filterable TDS.

               After the TDS results were known, a conductivity test was performed. A
        value was then determine to multiply against the conductivity to get as close as possible
        to the known TDS.  If a value is not known, the default value, always being around of
        .64.  The city of Chicago’s value at one time was .53. Hillsborough County, Florida where
        Tampa is located, is .63.  All cities will have a conversion factor from conductivity to
        TDS.  In the mean time if you do not have one, use a conversion factor the default of .64.
               Conductivity meters will always have 2 metal probes to measure the circuit;
        the amount of electric current that they give off in the water. What are called cations
        have a positive charge +. Anions have a negative charge - .
               Examples of cations with a positive charge (+) are Sodium, Potassium,
        Calcium and Magnesium (there are many others) the anions have a negative charge (–).
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