ammonium!

just wanted to see if anyone agrees there is a serious absence of the mention of ammonium in mainstream fish keeping , why does ammonia predominate ? i mean ammonia occurs above and at a pH of 7 and ammonium below and given that ammonia build-up cannot occur in water which has the slightest acidity so why does ammonium get such low attention?

tropi-paul wrote:

just wanted to see if anyone agrees there is a serious absence of the mention of ammonium in mainstream fish keeping , why does ammonia predominate ? i mean ammonia occurs above and at a pH of 7 and ammonium below and given that ammonia build-up cannot occur in water which has the slightest acidity so why does ammonium get such low attention?

See..... www.irishfishkeepers.com/index.php/fforu...-ammonia-calculation

But, where did you get that ammonia only occurs at pH >7. That is not true.

It is a weak base with a standard pKa of about 9.2 in water. So under standard chemical conditions, at pH of 9.2 50% is unionised ammonia and 50% exists as ammonium.

Now, as ammonia is a weak base and ammonium is therefore a weak acid they will contribute to the pH which will affect their equilibrium if their concentration is high enough to have a considerable effect on pH.

Another thing that people keep getting wrong is that it is not just pH at which the proportion of ammonium to ammonia changes: temperature also causes quite significant changes.

Different test systems analyse ammonia by different means. Some measure TOTAL ammonia (ie unionised ammonia plus ammonium), other only measure unionised ammonia.

Now, ammonium is toxic, but under the basic principles of toxicology everything is a poison, nothing is not a poison, it the dose that counts.
In that, the dose of unionised ammonia that causes significant biological damage is very very much lower than the dose of ammonium to cause significant biological damage.

Ian

are you familiar with Dr.Rudiger Riehl and Hans A. Baensch? its their work I learned that from a while ago maybe somewhat out of date? yes why is it that temperature is so ignored especially in the context of people going to a lfs with a water sample only to get inaccurate results because they havent got the sample at the same temperature as their tank

I'm very much aware of Baensch. Great classic books.
the books are not out of date as the chemistry in them is the same today as it was then.
But the book is not PhD level chemistry !!

The reality is that water chemistry is rather complex.
There are different levels of teaching or explaining chemistry....but at the end of the day, even if the reader doesn't want to know the full ins and outs, the fish DO want to know the ins and outs of their water chemistry.

I don't carry around the LD50s of every chemical, I can't remember off hand the LD50 of ammonium, but ammonium is so low that the toxic effects of the anion associated with it may be the main toxic component (eg nitrate).

However, even if ammonium has a much higher LD50 (lethal dose that kills 50% of test subjects) than ammonia it will still affect the RedOx system and other water parameters that have a physiological/biochemical effect.

Often ignored in ammonia poisoning is that a fish can have ammonia poisoning even if ammonia is hardly detected within the water....why?
Apart from a few fish (eg some species of mudskippers) ammonia passively diffuses across the gills down its concentration gradient. However, there are other components involved.
If those other parameters/components do not favour the passive diffusion of ammonia then ammonia will remain within the fish and kill it.
Hence, a fish can show signs of ammonia poisoning even if there is no ammonia detected in the water.

Chemistry is all about balance....you can't have one thing without something balancing it.

ian

what is particularly succeptable to ammonium then or does the vast majority of organisms in a tank have the same tolerances with unionised ammonia and ammonium,not that ive any problems but also what is your suggestion for an ammonia treatment and test from a chemistry perspective?

what would keep the ammonia from diffusing across the membrane in them cases ? would it be with regards to another chemical creating a higher concentration preventing it ?

There is a difference in tolerance between species.
Fish such as salmon, sturgeons are not very tolerant of ammonia; but goldfish and mudskippers can do some special biochemistry to tolerate a higher level.

Detoxification or removal of ammonia is very energy and water conservation expensive. It has to be done, and there is a great deal of work done by organisms on the various strategies on getting rid of it.

In freshwater fish, the main route to getting rid of ammonia is by passive diffusion across the gill....but that requires copious amounts of water.
Marine fish do not have copious amounts of water at their disposal...so they convert ammonia into something else (dimethyl amine for teleosts, and urea for sharks).

pH, ammonia and ammonium levels in water, sodium ion content, RedOx and ionic balance, and water concentration all affect the method and energetics of ammonia removal.

If, in freshwater fish, the passive diffusion of ammonia out of the gill does not produce enough free energy or the entropy is increased then ammonia movement out of the fish will not be favoured unless the fish can actively transport it using free energy from metabolism (but few freshwater fish have that facility....mudskippers are ones that do).

ian

so in short fish dont really posses the ability to diffuse across the concentration gradient in their gills in the same way we do past the loop of henle in our kidneys?

I'm not going to write a comparative essay on this now.... I'm off to see some bargains in the wicklow mountains in a minute or 2.

The human kidney is very energy expensive (that is why it is hot). Removal of ammonia from amines (eg amino acids) is of the utmost importance for cell survival, and the removal of the amine metabolites is key.
We need to conserve water, pure ammonia requires immense amounts of water to remove...hence we don't excrete ammonia.
The kidney works by a counter-current system, and uses active pumps requiring ATP. Hence, energy expensive.

Life on land is a balancing act of conserving water vs conserving energy.

For us, that is why we need a low protein to carbohydrate ratio in our diet else too much protein stunts growth. (too much protein means we need much more ATP driven energy to get rid of the amine wastes).
For fish, the water acts to support their body weight...and hence they do not need that extra energy from carbohydrates to do their balancing acts.

In freshwater fish, very little ammonia waste is excreted in their urine....it mainly comes out the gills and the diffusion is a normally a downhill drive of the concentration gradient (ie normally they do not need to waste too much energy on getting rid of amine wastes).
In marine fish the situation is different.....they can't afford to lose water, so passive diffusion of ammonia out of the gills is not a good option.

But fish do have kidneys....and often we do see kidney damage as being a notable cause of fish loss in aquariums.

The full story is a bit more complex.

ian

complex? my kind of story , i'll look into when i get the chance so ! thanks