Re: mixing water

[IDMiamiBob@aol.com]

Graham writes:

> Something I've recently read about RO water is that it is actually too
>  pure to sustain life and therefore nutrients should be added to it. By
>  adding tap water you are effectively diluting the salts, not restoring
>  them fully. All life needs various elements, even copper! 
  
Welcome to the list, Graham.  Pure RO does lack the balance nesessary for the
vast majority of fishes, and can be hard on the fishes' metabolism.  Some fish
have evolved to maintain their internal water/mineral balance by exuding
excess salts, marine fish being prime examples, and possibly also rift lake
fish to some extent.  Most freshwater fish have to keep minerals and salts in,
and rid themselves of excess water.  They are in a continuous battle with the
natural forces of osmosis, which will cause their bodies to dilute.  Some
mineral content is therefore a good idea.

Some fish, like Diicrossus filamentosus have adjusted to water so soft that
they will only spawn at hardness levels of less than 10ppm.  I wish I could
remember the conductivity these fish are adapted to.  It is frighteningly low.
They are so adept at maintaining their internal water levels that pure
distilled water will not bother them at all

>  Domestic water softeners are a no-no as they add sodium ions, so
>  apparently, aquatic softeners must do it differently (though they must
>  exchange one ion for another).

Don't count on it.  There are a number of softener "pillows" on the market
aimed at unsuspecting fishkeepers that are just that.  Caveat emptor.

> Is this the same for rechargeable nitrate
>  removing resins (i.e. replacing nitrate with sodium) ?

Nope.  Nitrate has a negative ionic charge, and Ca, Mg, and Na have positive
charges.  Some nitrate removers work by adsorptyion, getting the ions to cling
to the surface of the granules.  Others replace it with something considered
(by whom I always wondered) less harmful.  Water changes and plants always
seemed safer alternatives to me.

As for the original question on the thread- yes, use the untreated tap water
to reconstitute your RO.  At 5% tap, your GH should be right in the correct
range for apistos.  The sodium content of your softened water will not give
you what you are looking for.  While commercial RO reconstituters are
certainly safe, I have never been an advocate of using something "artificially
contrived", especially when something more natural (if our municipal water
systems can be called that) is not only cheaper, but also less likelly to
contain so-called secret ingredients.  You can get a water quality report from
your local town hall for free that will tell you everything you need to know
about your water.
Bob Dixon


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