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RE: musings on water changes: pH change and Osmotic stress

Hi Wright

Were did Scheel write about this stuff?  I am interested in getting a hold
of the literature.

I just conducted an experiment with shipping zebrafish.  I had been shipping
25 fish / 1.5 Liters and a few people I sent fish to were a little concerned
with the densities so I tested it.  After the test the fish were acclimated
back to the system water, they showed no signs of stress going from 6.57 pH
to 7.8 pH in one hour as long as all the other parameters were the same.

Here is the jist of what was done:

Adult Zebrafish Shipping Protocol Test
David Lains 17 VII 02

This test was conducted to ascertain the effectiveness of our shipping
procedures for adult Zebrafish.  The fish were packaged in 1.5 liters of
fish water (28.5 °C, 500 microS, 7.8 pH,  8 ppm Dissolved Oxygen) with
0.25ml of Amquel and pure Oxygen filling 2/3 of the bag volume.  The bags of
fish were place two per box in Polyfoam Styrofoam insulated shipping boxes
with packing peanuts filling the gaps.

The packaged fish were left in the boxes for 24 hours with occasional ruff
handling to simulate being shipped.  After the 24 hours the fish were
unpacked and water samples were taken.  The water quality parameters are
displayed in the chart below.

Fish / Bag	Fish Weight	pH	Conductivity	Dissolved O2	Temperature
15		4.15 g	6.80	537 microS		27.5 ppm		24.3 °C
20		5.59 g	6.68	561 microS		25.3 ppm		24.2 °C
25		6.50 g	6.63	544 microS		24.7 ppm		24.4 °C
30		8.20 g	6.57	554 microS		23.9 ppm		24.3 °C

The fish were then acclimated by floating each open bag in an aquarium to
equilibrate temperature.  Immediately upon floating aquarium water was
introduce to the bags in 500 ml increments and then every 30 minutes until
the shipping water was doubled (total acclimation time: 1 hour).

The fish were then released into the aquaria and appeared to be healthy and
active.  They were then allowed to recuperate for two weeks before breeding
was attempted.  All groups produced similar quantities of embryos per
Best fishes
David Lains

><{{{>The real importance of tds is its close relationship to
><{{{>osmosis and the
><{{{>bad effect on fish if they are subject to abrupt changes in osmotic
><{{{>pressure (this was once the old pH mythology, that was discredited by
><{{{>Scheel and others many years ago -- still shows up in books,
><{{{>anyway). It
><{{{>matters little if the tds is in dead soft water (e.g., a lot
><{{{>of salt) or
><{{{>very hard water (lots of CaCO3 equiv.), if you suddenly drop
><{{{>the tds it
><{{{>can damage gills and skin and cause all kinds of disease
><{{{>outbreaks, even
><{{{>if it does not kill the fish at once. Osmosis seems amazingly
><{{{>about *what* the particular ions are, just how much pressure
><{{{>is caused
><{{{>by the dissolved stuff.
><{{{>Other tank chemistry and biological processes may be very
><{{{>dependent on
><{{{>the exact makeup of the dissolved solids. That is taking us
><{{{>where George
><{{{>was getting frustrated, so I'll just leave it there. :-)
><{{{>Avoid tds shock by doing smaller changes more often.
><{{{>PS. Simple version for George: "Water changes are good." :-)
><{{{>"Deport all the product-liability lawyers to Iraq;"
><{{{>                                 -- Dave Barry --
><{{{>       [Best suggestion of 2002, by far...]
><{{{>              <www.sfbaka.net>
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