Re: RE: NANFA-- TDS and Conductivity
Sat, 21 Oct 2000 13:19:57 EDT

In a message dated 10/19/00 5:31:01 PM, writes:

<< But since I shouldn't really CARE what TDS is,
because conductivity is the preferred measurement, then I should
be happy. >>

You really care what the TDS and conductivity is by comparison only. That is,
whether the TDS of a shipment or collection of new fishes is close to what
you have available in your tanks or your water supply. While some species are
very particular, most don't care as long as the change is not sudden and
dramatic. I use both a conductivity meter and a TDS meter interchangeably and
the conversion factor for all natural waters that I have tested is about 1.8.
That is 1.8 times the TDS reading equals the conductivity reading. Both are
calibrated with potassium chloride solution which has a conversion factor of
The change in TDS or conductivity when switching water is much more
critical when they are going from high readings to low readings because the
change in osmotic pressure in that direction will burst their gills if too
much. A lowering by 1/2 over a 24 hour period is about as much as should be
attempted. On the other hand you could double it within minutes without any

Lee Harper

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