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GARGAS: Water and the Aquarium                Page 6

        Examples of them are Bicarbonate, Chloride, Phosphate, Sulfate (there are many others).
        Cations and anions complete a circuit so they give a conductivity reading.
               Conductivity meters are available to measure in two numerical ranges; one is
        in MicroSiemens (μS) the second is MilliSiemens (mS). For freshwater it is easier to
        use MicroSiemens. The symbol for MicroSiemens is a small u and a large S (μS). The
        Symbol for MilliSiemens is a small m and large S (mS). MilliSiemens are used if the
        conductivity is above 2000 MicroSiemens. Swimming pools and saltwater aquaria will
        need a meter that reads in mS (MilliSiemens). Saltwater swimming pools that use a cell
        require conductivity in the range of 6-8 MilliSiemens. FYI:  1 MilliSiemens = 1000
        MicroSiemens (6 MilliSiemens = 6000 MicroSiemens)
               Ok so we know a bit about TDS and Conductivity. What does that mean to
        the Aquarist?  Zoos and public aquariums will all agree that when you keep captive
        animals you need to have an environment as close as possible to the natural
        environment that the species come from. With tropical fish it is no different. Rainforest
                Aphyosemion australeE
        species must have a water quality of a rain forest. Lake species from the Rift Lakes in
                                                    Young Koi From
        Africa have a water quality much different than rain forest species.
                                                    Steve Rybicki
               Ok we need to get from conductivity to TDS to Osmotic pressure.
            by Hank Darin
               Osmotic pressure is the hydrostatic pressure produced by a difference in
                                                    Photos: MFJacobs
        concentration between solutions on the two sides of a surface such as a semi permeable
        membrane or cell (Ed: or for instance the cell on the gill of a freshwater fish and the
        surrounding water). Osmotic pressure also occurs in and around freshwater fish as they
        must keep on osmoregulating . . . spending much energy retaining salts and excreting
        We tested the tap water in Sarasota, Florida in a 10 gallon tank with.

        The conductivitwas 670 μS (MicroSiemens):
        670 x (multiply) by .64 (We do not have a conversion from Sarasota Water Dept.)
        670 X .64 =  gives us an approximate TDS value of 428.80 mg/l  or ppm.

               Now we take the TDS and divide it by 100 to get the Osmotic Pressure:

         428.80 100 4.28÷  =  lbs per square inch Osmotic Pressure.

               Some fish species can tolerate higher Conductivity, TDS and Osmotic
        Pressures than others in comparison to their natural habitat. What makes matters
        worse, though, is when aquarium salt and other additives are added to the aquarium . . .
        not only does the conductivity increase but now the ions that were in balance in the
        natural water (tap water or water source) are completely out of balance.
               To explain this better ionic imbalance occurs when Chloride and or Sodium
        become the major cations or anions in water. then it becomes imbalanced and unnatural.
        If you look at just about all fresh waters with very few exceptions it is calcium and or
        magnesium that are the major cations and sulfate, alkalinity/bicarbonate/ carbonate are
        the major anoins. Even in Lake Tanganyika which is the biggest exception to the
        freshwater rule the principle cation is magnesium and the major anion is bicarbonate/
        carbonate. These ions even though they are water soluble they are much less soluble
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        than the chloride and sodium ions. All aquarium additives have one thing in common:
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