"Charlotte & Carsten" <Herfoelge@Andersen.tdcadsl.dk> skrev i en meddelelse news:3d95addf$0$18133$edfadb0f@dspool01.news.tele.dk...
> Hej i NG.
>
> har et sted læst at man kan komme en smule salt i sit akvarium, men kan ikke
> huske hvor meget pr liter og hvorfor.
>
>
> --
> Med venlig hilsen
> Charlotte & Carsten
From: "Nestor 10" <nestor10@mindspring.chkr.com>approach...
--
-Y-
http://www.mindspring.com/~nestor10
nestor10@mindspring.chkr.com
".chkr" is for mail- bots
-------------------------------------
Dave Darsow wrote in message news:36b7572a.0@news.netwalk.com...
>...i have found that using salt tends to keep the fish healthier.
>there are several reasons for this:
>1. salt adds electrolites to the water which allows the fish to
>maintain their slime coating naturally...
The addition of electrolytes also increases conductivity, which is one of
the reasons they have that name. An increase in conductivity is most usually
coupled with an increase in osmotic pressure differentials. But that can
wait 'til your point number two.
As to facilitating slime production, could this not also be an indicator of
an added stressor? Diagnoses of contagion, parasitic or chemical influences
often rely on the amount of slime produced, particularly any increases.
Fishes unaccustomed to increased TDS levels or the types of solids involved
may simply be reacting to an irritant.
>...it also improves the functioning of thgills for better absorption
>of dissolved oxygen.
Usually in an environment overly-abundant in nitrogenous compounds. But
then, it doesn't "improve" the functioning of the gills, either - it
competes for passage through them to the bloodstream, and the effects of
nitrogen poisoning are merely diminished by default.
>2. it is a well known fact of basic chemistry that moisture
>moves from an area of lesser salinity to an area of greater
>salinity. fish have salt in their bodies, if the water has no salt
>then the fish are constantly having to fight off water soaking
>into their bodies. by using salt it decreases the amount of
>stress the fish are under. in marine fish it is just the opposite,
>the water contains much more salt than the fishes bodies, to
>compensate for this marine fish are constantly drinking water
>and urinating to rid their bodies of excess salt and keep from
>dehydrating.
Most biochemical and biomechanical processes are in place to serve a useful
purpose, tailored to specific environmental conditions. And because it is a
natural, on-going function it is subject to some degree of fluctuation in
the real world. This means a degree of flexibility is also involved, but
doesn't negate the concepts of optimal ranges. Recommended salt additions
stretch from "tonic" levels of one teaspoon per five gallons through dosages
of up to two teaspoons per single gallon stated for some nitrogen-sensitive
fish. So, in round-robin fashion, the aquarist must first decide upon the
efficacy of its use and the size of the dosage, which brings one back to
determining the amount of salt and minerals in the fish's native habitat.
Not so hard to do when dealing with a species tank, but community tanks are
often a hodge-podge of fish from what may even be competing environments, in
turn leading to differing tolerance levels and the choice of which fish to
irritate the least.
>3. salt also increases what is called the surface tension of
>the water which helps suspended particles to sink and tends
>to create a clearer tank. this is the main reason that marine
>tanks tend to be much clearer than freshwater.
Don't know that I can fault this point.
The increased surface tension helps to clear the water by allowing a wider
selection of materials to bind together. They form "clumps" whose combined
masses eventually overcome the added bouyancy of increasing the specific
gravity with salinity. I say that only to tie surface tension with the
clarity though.
::::::::::::::::::::
The use of salt in the aquarium harkens back to the days of little or no
knowledge of the intricacies of the nitrogen "cycle" and effective
filtration methods. The term "aged water" is a carry-over from the period
that well illustrates the point, even when examining the change in meaning
that has accompanied it.
We bandy phrases such as "new tank syndrome" about with comfortable ease
today, confident in the knowledge that each phase is predictable and
explainable. "What's waste to one is feast to another," we say, explaining
how decay creates a "reverse" food chain from proteins all the way back to
nitrogen and water. Just two to three decades back, however, it was still a
mystery to the largest part of the hobby. Water that had been conditioned by
prolonged contact with the fish was considered safer than fresh water,
working through incorrect assumptions on observations with new,
freshly-established tanks. Even though it was understood that some portion
of the water must be regularly changed, as much as possible of the "aged"
water was conserved. This also held true for the first few critical weeks of
a new tank...
The problem with elevated nitrogen levels in the tank occurs in the blood.
The most critical phase is during the normal nitrite spike, but still
happens to some degree with a build-up of high nitrates. Nitrite as an
anion, NO2-, oxidizes the iron in hemoglobin, directly affecting oxygen
transportation. It affects the blood after absorption through the gills,
which happens to be the weakest point of the process. It can be blocked at
the gills by increasing the concentration of chloride anions, Cl-, whose
similar shape and charge cause them to seek the same pathways as the
nitrites. And the chlorides have a slightly easier time fitting those
pathways, effectively crowding out the opposition.
Thus, the hobby learned to cope with the "necessary evil" of nitrogens in
order to maximize on-hand quantities of that precious "aged" water. This is
no longer necessary or desirable, and the freshest possible water has become
the new goal. Today, we simply "age" our municipal water supply overnight to
outgas the chlorine.
I am neither a supporter or detractor for the practice of salted aquaria - I
could probably formulate equal pro and con columns on a balance sheet with
it. It could be a crutch during cycling for a newbie, but so could water
changes. It could ease the maintenance of a overly-varied or overly-stocked
community aquarium, but so could restricting your choice of fish to those
naturally suited to your water and the size of your tank. The list goes on,
but the choice boils down to one thing - personal tastes and preferences.
The same things that affect changing frequencies, feeding schedules, yadda,
yadda, yadda.
The best way to keep the subject neutral is through an accurate accounting
of the facts involved...
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From: "Nestor 10" <nestor10@mindspring.chkr.com>> ...since I use salt
(diluted seawater)in my quarantine system...
Here's the main crux of the debate. There's a considerable difference
between using salt as a disease treatment or quarantine standard than in
*keeping* salt in the aquarium as a permanent *tonic*. By far, when someone
pops up on these newsgroups and asks the question, it's not in the form of
treatment but in maintaining the long-term health of the tank's inhabitants
through continual dosing.
There's little merit in arguing against salt as a short-term therapeutic
agent - it's been proven effective in such an instance. However, quite a few
of the properties that make it useful in the short term against pathogens
can also turn the tables against you as a permanent addition to a tank in
cases where specific fish do not encounter these levels in a natural
habitat. In other cases, a more natural approach can achieve results that
surpass the percieved benefits of salt addition.
Take, for example, your statement:
> ...Salt also has the added benefit of reducing osmotic stress
> and nitrite toxicity...
Nitrite toxicity is the easiest to handle, so we'll start with it. The
nitrite ion, upon entering the bloodstream through the gills, oxidizes the
iron within the hemoglobin to produce methemoglobin. This severely limits
the bloods ability to transport oxygen, causing the fish to display symptoms
of hypoxia in ever-increasing increments until it simply suffocates. There
are a host of other ills and symptoms associated with long-term hypoxia, but
suffice it to say that none are beneficial. The nitrite ion easily finds its
way into the bloodstream because the gills essentially expose the
bloodstream directly to the source.
An intersting thing happens when you add salt to the water. As it hydrates
into solution and dissociates into sodium and chloride ions, the gills are,
of course, exposed to the solution. Exchange sites at the gills are then
presented with a choice of passing either the nitrite ion or the chloride
atom, and guess what? Due to the similar size and charge of the chloride
ion, combined with its specific mono-atomic shape, the chloride atom passes
more easily than the more complex nitrite ion. The nitrite ion's charge,
though equal in strength, is a little "lopsided" by the placement of the
hydrogen atoms in relation to the nitrogen. It's not an evenly distributed
charge. The end result is an increased affinity for the chloride over the
nitrite, essentially blocking the nitrite and preventing the change in
hemoglobin on the same scale as unsalted water.
But why put the fish through this to begin with? Instead of adding one
chemical in the hopes of reducing the effects of another, wouldn't it make
more sense to simply remove the offending compound? Isn't that what fresh
water changes are all about?
Moving on to "reducing osmotic stress"...
Now *there's* a move that makes the term oxymoron more literal than was
intended through Webster.
Osmotic pressures are determined directly through the concentrations of
dissolved solids within the water. The most commonly used factor is to
divide the mg/l measurement by 100 in order to determine osmotic pressure in
pounds per square inch, so let's use that to examine the effects of salt
addition to my own local water. We'll even go for the low end of your
therapeutic dosage of "~2,368 ppm" using the "standard 1 teaspoon/gallon".
According to the Tennessee-American Water Company's 18th annual report on
water quality, the average measurement of TDS in my water supply is 94 mg/l,
giving an osmotic pressure of 0.94 lbs/in2. I now add salt to increase the
TDS by 2,368 ppm, and converting to like units also gives me 2,368 mg/l. So
I now have a TDS reading in the neighborhood of 2,462 mg/l, raising the
osmotic differential to 24.62 lbs/in2.
Let's back this up with a simple experiment. Hold on a second while I mix
some water and test it with my handy-dandy PinPoint Conductivity meter...
OK, I'm back. The initial reading on straight tap water was 182 µS, and
after adding a lightly-packed, level teaspoon of Instant Ocean I now have a
reading of 2.77K µS.
The simple addition of a teaspoon of salt per gallon of water has increased
the osmotic pressure by a factor of slightly over 15-fold! I'm sorry, but I
completely fail to see just how this can accomplish the reduction of osmotic
stress.
Why is osmotic pressure important to begin with? Well, water retention
within cell structures and salt levels within the body spring easily to
mind. Fish native to mineral-poor waters are the most highly adapted at
retaining salts while rejecting water in order to prevent bloating within
the cells. Subjecting such a fish to osmotic pressures in excess of
multiples of a full order of magnitude puts a significant strain on the
body's resources, wouldn't you say?
So again I ask - how does this bring about a reduction of osmotic stress?
And just *how* is salt proven beneficial in the control of certain diseases
and parasites to begin with? Simply put, by creating such increases in
osmotic pressures and, in effect, "dessicating" the organism involved -
water retention capabilities are stressed beyond the point of being able to
cope with the increased pressure differential and necessary water is driven
from the cells.
So when adding salt, you're faced with the same basic decisions as is a
doctor when using antibiotics or chemotherapy:
How much, and at what duration, will prove fatal to the pathogen without
destroying the host?
And all this without even touching on such oft-repeated arguements such as
increased slime production, etc., etc...
--
-Y-
http://www.mindspring.com/~nestor10
nestor10@mindspring.chkr.com
".chkr" is for mail-bots
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