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Re: Lowering pH when adding hard water nutrients to soft water

On Mon, 4 Sep 2000, David Youngker wrote:
> > Date: Sun, 3 Sep 2000 17:06:42 -0400
> > From: Kevin Zippel
> >
> > ...As an update to my cellar chemistry experiments, after
> > only 8 water changes in just 4 months, the conductivity in
> > the tap-water topoff bucket is 502 (233% of initial), and in
> > the RO topoff bucket it's 223 (104% of initial).
> > I'd say it's fairly important.  Kevin
> I'd say its importance lies in overemphasizing the results. There aren't
> many aquarists (I, fortunately, know of none personally) who let 20% of
> their tank evaporate and then simply top it off.
> Tell us again - how quickly will a lab rat develop cancer drinking 22,000
> diet Cokes a day? ;-)

You don't have to let 20% of you water evaporate to see an effect. Several
of my tanks have been in continuous operation for years. After a few years
of 15% weekly changes I've measured specific conductance in my tanks
approaching twice the value in my tap water.  Specific conductance is a
semi-quantitative measure of salt content.

Salt concentrations will tend to rise over time to the point where the
amount of salts you remove during one water change is equal to the amount
you add to the tank with water changes, or between changes with top up,
fertilizing, feeding, medication and so on.  In my house, the older the
tank, the higher the salt content.

I don't keep or breed fish that are sensitive to salt content, so I don't
worry about this buildup. If I were breeding sensitive fish in tanks that
I kept running for years -- or in tanks where I added a lot of dissolved
salts -- then I'd seriously consider doing the occasional very large water
change.  That would help offset the increase in salt content over time.
Just using RO for top-up doesn't do the whole job, because it doesn't
offset the salt that comes from sources other than water changes.

The salt content would have to get awfully high before is became a
problem for the plants. 

Roger Miller