ALL THINGS KOI AND H2O
AMMONIA NH3 THE ENEMY WITHIN
By D Griffiths 14.11.2001
Koi are termed Ammonotelic. Meaning most
of their nitrogenous waste is excreted as Ammonia gas, rather than Uric Acid.
In a closed pond system this presents many problems to aquatic life forms
but not least the koi.
Ammonia is primarily produced by the koi in the typical pond system and to
a lesser degree by other by processes found in the pond system.( faeces etc)
It is found in two forms free Ammonia NH3+ (un-ionised, free Ammonia) and
Ammonium NH4+(ionised Ammonia), the former if which is considered the more
toxic form.
Ammonia is dealt with in the pond system by a vast number of nitrifying bacteria
in our biological filters; this process is termed the nitrogen cycle.
Ammonia NH3/4 is oxidised by nitrifying bacteria to become Nitrite No2, which
as far as we as koi keepers are cocerned is just as toxic, but a second colony
of Nitrifying bacteria oxidise this to the less toxic Nitrate NO3 roughly,
about a hundred times less toxic than Ammonia.
As Ammonia is subject to lower ph levels below 7, it picks up a Proton and
is ionised to form Ammonium NH4+, however if the ph rises again it is also
capable of dropping the Proton to once again become Ammonia NH3+.
Most test kits available measure total Ammonia Nitrogen, which will be the
combination of both forms,Ammonia and Ammonium.
The higher the ph of the water in the system, the greater the percentage of
un-ionised, free Ammonia there will be and the lower the ph the more ionised
Ammonium there is.
In a well set up mature filter/pond system, we should expect and only accept
finds of very low or undetectable levels of Ammonia when we test for this
substance, therefore it serves little purpose to test for which form of Ammonia
you have, since if we also know the ponds ph we should have a greater understanding
which is the predominant form of Ammonia there is NH3 or NH4.
Measurable amounts of Ammonia from a typical test kits indicates something
is very much amiss and investigations should begin in earnest to determine
the root course and remedial rectification should begin at once Anything but,
un-measurable, low, Ammonia readings should not be tolerated in a mature pond.
The general acceptable back ground level ammonia reading should be below 0.02mg/L
You would be tempted to think the koi was in harms way from any and all Ammonia
in its surrounding water, and you would be right, I'm sure you have all smelt
Ammonia in it rawest form (most commercially produced window cleaner etc)
obnoxious is about the nicest thing you can say about Ammonia, it makes you
eyes water and burns the nasal cavity and throat and takes your breath away.
It may surprise you to know the exact same symptoms effect a koi, only the
koi is a lot more sensitive to its effects, additionally, unless the keeper
takes action, the koi cannot escape the effects of Ammonia and will be subject
to burns to gills, skin, fins and the koi will be stressed beyond belief.
But as the title of this paper insinuates, something else is going on of equally
danger to the well being of the koi.
A koi eliminates waste nitrogen as Ammonia gas mainly via the gill lamellae.
The koi's blood is very slightly acidic, and there are reason for this phenomena,
but the ammonia produced by the koi will be in the form of NH4+, ammonium.
This process is termed Osmosis and diffusion.
People often think of Osmosis and Diffusion in terms of body fluids and salt,
moving from one side of the koi to the other via the gill but in fact almost
anything dissolved into fluid /water can migrate via the osmotic/diffusion
process provided the molecule is not to large to pass through the holes in
the membraneit's traveling across,
OSMOSIS
(Osmosis is when a fluid moves across a membrane from a high to a lower pressure
to equalize.)
Osmosis ceases to happen when the two concentrations each side of the membrane
achieve equal pressure,
Diffusion
Diffusion is when a dissolved substance moves across a membrane to equalize
the concentration; this is termed an Isotonic state.
A saline concentration that is higher outside the koi to its internal concentration
is termed Hypertonic state.
A lower salineconcentration outside the koi is termed Hypotonic state.
A Hypotonic and Hypertonic state will try to achieve Isotonic status,
provided the membrane is at least semi-permeable and the molecule involved
is not too large to pass through.
The method of waste removal (Osmoregulation) presents certain inherent problems
to the koi. If you subscribe to the theory that the majority of Ammonia in
the pond is being produced as a by-product from hungry koi via the gill( and
this will be the case; unless something is sadly amiss with the pond / filtration
system), it follow that the koi is the major source and in order for the koi
to rid itself of this toxin the target for the unwanted Ammonia is the pond
water.
Unlike Nitrite (NO2) Ammonia NH3/4 the source is in the main the fish and
the pond water the target, Nitrite NO2 however the source is the pond and
the fish is the target.
With the process of osmosis/diffusion, the target for Nitrite has to be the
internal body fluid of the koi via the gill lamellae because the pond is always
the higher cocentration but with ammonia its the reverse.
So you could say in the *natural* sequence of events in a typical pond is,
the Ammonia is trying to get out of the fish into the pond and Nitrite is
trying to get into the fish from the pond.
Most folks think of running high Ammonia levels in the same light as Nitrite,
in so much as its perceived as physically damaging the fish from the outside
also to be attempting to enter the fish, and once there will do still more
serious damage the fish. The answer to this one is YES and NO,
Yes the ammonia will be doing sever damage, irritation and stress to the koi,
which in itself has serious enough consequences. But the Ammonia is not trying
to get inside the koi, because the koi is the source of the Ammonia and the
physics attached to the rules of diffusion dictates that as the Ammonia level
rises in the koi's tissue fluids, it is trying to get out of the koi and the
best case scenario for the koi is equal concentrations inside to outside.
example, if the pond water is running at a level of Ammonia @1mg/L the way
diffusion works, it will be a fact that the level of Ammonia in the koi's
fluid will be around the same because the koi is the source and can only release
it to equal concentrations, So it follows that if the ambient Ammonia in the
pond is almost zero the koi can release Ammonia to that self same level, and
if for some reason the filter is new and immature or has stalled or simply
can't cope with the organic load placed upon it, as the koi releases still
more Ammonia into the water and the Ammonia level rises in the pond and the
filter is not clearing it, so the level of Ammonia *IN* the koi rises to match
the external concentration.
If it helps, try to visualize it as two empty containers side by side each
chamber connected at the bottom by a tube with a fine membrane across the
tube, separating the two chambers, pour a pint of water (which represents
the koi's body fluid) into one of the containers, (this container will represent
the koi), this will increase the pressure in the one chamber. As soon as it
can, that pint will displace into the other container (which is representing
the pond), you end up with equal measures/pressures in each container. We
then add still more body fluid, (another pint of water) and end up with one
pint in each container. And the membrane is called the pressure point. This
is Osmosis.
Still with the pint of water still in each chamber dissolve two ounces of
salt into the side representing the koi, and over a period of time without
moving any water the salt will diffuse across the membrane to the lower concentration
or into the non saline chamber, till you end up with the equivalent of 1 ounce
per pint in each side
This is the Diffusion.
In reality both the above work at the same time as the salt moves one way
the water moves the other, this is termed,Osmoregulation
So you can see from the diffusion example
if we substitute ammonia for the salt, that as the koi is the source of Ammonia,
it can never be lower in Ammonia content than the concentration of the pond.
This is the principle of Diffusioni.
You may now be forming a differing opinion as to if it's the external Ammonia
or the internal Ammonia that will eventually kill the koi.
If Ammonia levels are allowed to run continually high in the pond, I think
the true answer would be more of the internal but not excluding the external
level of Ammonia that will also contribute its fair share of damage.
This may help explain the anomaly of some claims that, when a koi is being
transported in shipping bags over long distances from Japan, where by the
koi dump huge amounts of Ammonia into a limited unfiltered amount of water
in the transport bag. Some people claim the koi is able to reabsorb Ammonia
from the water as a safety valve to keep it from harm, and will dump this
accumulated Ammonia at the first opportunity when conditions are correct for
it to do so.
Under the principles of Diffusion it's just not possible for a koi to reabsorb
Ammonia from the bag water as it is always trying to add to it, in fact, as
the Ammonia level in the koi continually builds up to levels above the outside
concentration the koi will add to it, but not to the point were the outside
is higher, the two levels internal and external levels will rise steadily
together.
It is true that a koi, when conditions are right, i.e., in an non polluted
pond the koi will dump this excess accumulated Ammonia post haste, but this
is not the act of reabsorbing Ammonia, but rather retention of Ammonia. Two
very different things.
However there are conditions where a reverse of the osmoregulation system
can happen. If something else is adding ammonia to the pond system faster
than the koi can (i.e. rotting vegetation, algae, food, etc, this could lead
to I higher concentration of ammonia being outside the koi and in this instance
the ammonia would reverse its way into the koi being as the koi is now the
lower concentration.
The above gives a clear explanation of how a koi rids itself of Ammonia but
the koi is as much at risk from the accumulating amounts of Ammonia toxicity
internally as outside with high ambient Ammonia readings.
Therefore the koi is at risk from the enemy within.
.