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water change musings - Salt water treatment against bacteria

Hi Wright,

Sea water fish have a very active osmotic regulator system due to the fact
that they are a lot hypotonic compared to their environment. This means that
they have active salt pumps in all parts which are in contact with the
water. Reversely, they must counteract the osmotic pressure which will tend
to drain water out of their cells. Thus their water pumps are actively
pumping water from the water into the cells of their skin, eyes, mouth and
respiratory system.

Now they thus have active water pumps pumping water into their cells on one
side. On the other side if you suddenly dump them in sweet water or osmotic
water, the osmotic pressure reverses. Which means that osmosis now presses
water into the cells. Thus suddenly, the fish has 2 phenomena pumping water
into his cells: Osmosis and his biological water pumps.

I wouldn' like to be that fish!

On the other hand, protozoans bacteria and many small external parasites
will die much faster because they dont have an entire boddy to pick up the
surplus on water from the other side. All water that rushes into a bacteria
will blow it up like a ballon until it breaks.

The fish has water rushing into his skin and cells of his repiratory system,
thus the same phenomenon occurs, these cells get pumped like a balloon.
However on the other side of those cells, there is no water, but other
cells. This means that the rush of water will only come from that part of
the cell which is exposed to water. That is normally between 1/3 and 1/8th
part of the cell which is exposed to water. The other sides are surrounded
by other cells which partly will even pick up part of that excess water.

Bacteria and Protozoans dont have this advantage and they will die much
faster.

By the way, this is exactly what happen when you make a salt water short
bath to sweet water fish: You dump the fish in the salt water, his cells
first get drained of water (osmosis), then his cells pick up salt
(dialysis), then his cells adapt. The same will happen with bacteria and
protozoans. At the end of the treatment, they are saturated with salt and
have their normal size again. Many bacteria will already have left the skin
of the fish and be looking for a better environ. Thos who havent left the
fish and haven't died yet are now dumped again into the sweet water of the
tank, at a moment when they are saturated with salt. Osmosis presses now the
water into the cells (fish and bacteria). The fish cells can adapt much
better because they are enbedded in the organism. But the bacteria are
helpless. Water rushes into them, they go like a balloon and bang!

Erik

> -----Ursprüngliche Nachricht-----
> Von: owner-killietalk at aka_org [mailto:owner-killietalk at aka_org]Im
> Auftrag von Wright Huntley
> Gesendet: Sonntag, 28. Juli 2002 06:03
> An: killietalk at aka_org
> Betreff: Re: water change musings
>
>
> Hi Roger,
>
> Roger Hawthorne wrote:
> > Thank You Wright:
> >
> > My knowledge is based on what has worked for me
> > over the years, and conferring with hobbyists too.
> > But of I were to try and explain something, a real
> > knowledgeable person might laugh.
>
> Is *that* why I cause so many chuckles on the list. :-)
>
> >
> > This osmotic change may be what happens when I
> > give salt fish a freshwater dip, or vice versa. Am I
> > wright.. cuse me...right on that one, or wrong again?
>
> Vice versa works, but the salt fish into fresh water can sometimes be a
> horrible shock. Before the osmotic regulators can adjust, fresh water
> rushes into the cells and tries to dilute the salt of normal body
> fluids. The result can vary from simple distress to burst gill and skin
> cells and infections or death. Probably very species dependent.
>
> You can dunk a fresh water fish into sea water with less problems,
> usually. Apparently it dehydrates some cells before the osmotic barrier
> can adjust, but the results seem less permanent.
>
> ciao
>
> Wright
>
> --
> "Deport all the product-liability lawyers to Iraq;"
>                                  -- Dave Barry --
>        [Best suggestion of 2002, by far...]
>               <www.sfbaka.net>
>
>
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