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Re: chlorine, chloramines and sodium thiosulphate
Alberto Restrepo Ubach wrote:
> ... Now, another question for those of
> you with some knowledge of water chemistry:
> I have access to lots of sodium thiosulphate. As I understand it,
> that is the stuff out of which most 'old style' de-chlorinators were
> made. In other words it works great to neutralize chlorine. But now
> that the water supply of most metropolitan areas in the U.S.A.
> contains chloramines in significant amounts (i.e.: enough to kill my
> killies), is sodium thiosulphate of much use? Does it act on
> chloramines the same way it does on chlorine? Or does it have an
> adverse consequence? (I seem to remember a discussion some time ago
> in which someone suggested that the typical de-chlorinator was --at
> the very least-- useless for chloramines, and maybe even harmful.)
Charles Harrison and I have had many an enjoyable "discussion" about that
here. Since he is a real chemist, and I'm not, it makes for an uphill fight
for me every darned time. ;-)
Much of that difference has been a matter of degree, and what the particular
situation was. I have not always been explicit enough about the conditions
that bothered me. [Please forgive me if I get windy about those here.
Charles will just flay me, again, if I don't. <G>]
Hypo (thiosulfate) is often fine for partial water changes on adult fish in
well-aerated tanks. The small amount of released ammonium stays in that
form, mostly, and doesn't convert to very much nasty ammonia in most normal
water at any reasonable pH. So far, so good.
Unfortunately, EPA has mandated, in addition to chloramine, that many older
municipalities must add enough alkalis or base chemicals to their system to
bring pH up to around 8 or 9 to retard etching of lead and copper from older
pipes. This is mostly a problem in areas with naturally occurring soft, acid
water, and depends a lot on what they use. If it truly raises alkalinity, it
buffers, and makes for a problem with chloramine as we shall see.
Major fishroom wipeouts with hypo and chloramine have happened in situations
where 100% water changes are common, particularly in harder water areas,
where the tap water is buffered too well to allow any pH drop. Without the
usual nitrates, and other organics to drop the initially high pH, the burst
of ammonia was more than enough to be lethal. Betta and killy folks who do
100% changes on shoeboxes, jars or or small tanks were, by far, the worst
Between the "all dead the same day" incidents (I know, personally, of
several) and the relatively harmless situation lies a nebulous continuum of
conditions that can be aggravated by the burst of ammonia without killing
everyone off. Symptoms can be vague and often delayed for some time.
Baby fish get clubbing of the finer gill filaments and become permanently
stunted. Adult fish are temporarily, and sometimes permanently, sterilized.
Respiration can become labored as the gills are seared. General health can
be reduced, making diseases more common. [Ammonia exposure is a known
precursor of most bacterial gill diseases.] None are easy to spot, but these
are all things we do *not* want to do to our fish.
First, what level of ammonia is harmful? Spotte in his _Fish and
Invertebrate Culture_ cites references showing that a wide variety of
harmful effects result from various sub-lethal doses of ammonia. The amounts
for permanent damage are truly tiny, as low as 0.006 ppm of un-ionized
ammonia for baby fish. See pp 104-106 for a long list of references on the
problem. These effects are shown to not be species dependent, BTW, and apply
to most all teleosts about equally. [Killies are just so darned tough they
may be slower to *show* outward symptoms than some other fish, though.]
OK. One may well ask how much of the total ammonium/ammonia is in the
damaging un-ionized ammonia form? The equililibrium between ammonium and
ammonia changes smoothly between almost no ammonia well below pH=7 to quite
a lot at 8 and a whole lot at 9 (if we are concerned with only 0.006ppm).
For example, at those three pH levels and at 20C, the percent of the
combination as ammonia is only 0.5% at pH=7, but rises to almost ten times
that, 4.7%, at pH=8. It is 35.8% at pH=9 or over 70 times as much as at 7!
Essentially, more available hydrogens (H+) means more NH4+ ions and less
un-ionized NH3. Makes some sense. Since the number of available hydrogens
drops 10X for each pH point of increase, we might expect the equilibrium to
somewhat follow that pattern, and it does pretty much that.
Since we already know that 0.006ppm of ammonia is measurably harmful, we
want to stay well below that level. That means that the *total* measured
ammonium/ammonia, per your test kit, must be well below 0.128ppm to be safe
at pH=8 and 20C. Unfortunately, that level of combined ammoniums isn't even
detectable on most test kits, but can harm your fish, anyway. Babies could
be permanently damaged but older fish only temporarily stressed.
At pH of 7, it would take a reading of 1.2ppm to reach that same ammonia
level (0.5% of 1.2ppm= 0.006ppm). That, BTW, isn't very far from what some
domestic-water chloramine doses release when treated with sodium
The situation gets even worse at higher temperatures as the ionization
constant of water drops and the dissociation constant of ammonium increases.
It is further made worse by poor oxygenation and other factors that can
combine with ammonia to increase damage. The damage is sometimes recoverable
in older fish, but often permanent in small babies (where we are more likely
to do 100% changes, too).
Depending on how anal you are about your fish husbandry, the use of hypo on
chloramine should be pretty questionable, at best, and should be avoided,
like the plague, for treating water for new babies.
> And last BUT NOT LEAST, if sodium thiosulphate is not very useful
> given modern municipal water treatments, what chemical(s) are used in
> products like AmQuel to 'neutralize' (is that the right term?)
I'm not entirely enamored of them, either, for they are generally tanning
(protein cross-linking) agents very similar to formaldehyde. In small
amounts they apparently are harmless to fish, but they have other drawbacks
for the breeder.
All I have tested carefully (Prime, Amquel and Ammo Lock 2) kill small
invertebrates like daphnia, ostracods, moina, hydra and flatworms, just like
formaldehyde does. I concluded they probably also do that to a number of the
soft smallest ones we depend on for baby starter foods, like paramecia,
Interestingly, I have *not* noticed that they precipitate out the
free-swimming flagellants from green water (presumably Euglena species).
I use Amquel, generously, when shipping fish. Even when starved, a little
ammonia builds up and the ability to sequester it is useful there to
minimize stress. Otherwise, I use multiple carbon filters on both RO and tap
water to *very-slowly* remove the chloramine from the water before it is
stored for use. [Testing for chlorine between filters tells me when it is
time for a change.]
I can pull a tuft of Java moss from almost any of my tanks, put a drop of
Liquifry #1 on it, and generate a cloud of infusoria in a new hatchling
container in less than a day. When I used to use Amquel in all my tanks,
that was a much more iffy proposition, I think. It is always possible that
absence of dechloraminators makes my fishroom more sensitive to swimming
parasites like Ich or Velvet, but I have not observed that to be true.
Healthy fish are pretty good at resisting them, though, anyway.
Sorry Charles, but I guess my fishkeeping motto is slowly becoming "Better
things for better living *without* chemistry!" <VBG>
Wright Huntley, Fremont CA, USA, 510 494-8679 huntley1 at home_com
"Let us, for a moment, take the sex-education pushers at their word:
If you teach a child how to use a condom, you're promoting safety -- not
...Why, then, doesn't the same logic apply to guns?"
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