Relation between Free Ammonia and Total Ammonia

[Gfishery]

FA = Free Ammonia, TA = Total Ammonia

My humble attempt at understanding their relationship:
(am I even close?)

FA = 0 for pH < 7, (Free Ammonia can't exist under ph 7 ?)
FA = k*(ph-7)*TA , where 0 < k < 1 , and current pH > 7

If Free Ammonia depends on temperature as well, I suppose the formula
will be much more complicated.

[IDzine01]

There's a chemical reaction taking place.

In acidic water ammonia ions (NH3) react with water to create ammonium
ions (NH4+) and hydroxyl ions (OH-). When water is alkaline the
reaction goes the opposite way because, as there is already an
abundance of hydroxyl ions present in alkaline water. Instead of
creating ammonium (NH4+) out of ammonia (NH3) and water (H2O) they
hydroxyl ions (OH-) split from ammonium (NH4+) to create ammonia (NH3)
and water (H2O).

Did I confuse you? I confused me.

[Gfishery]

"IDzine01" > wrote in message
oups.com...
> There's a chemical reaction taking place.
>
> In acidic water ammonia ions (NH3) react with water to create ammonium
> ions (NH4+) and hydroxyl ions (OH-). When water is alkaline the
> reaction goes the opposite way because, as there is already an
> abundance of hydroxyl ions present in alkaline water. Instead of
> creating ammonium (NH4+) out of ammonia (NH3) and water (H2O) they
> hydroxyl ions (OH-) split from ammonium (NH4+) to create ammonia (NH3)
> and water (H2O).
>
> Did I confuse you? I confused me.

No, not totally. I have a fairly limited chemistry/biology background.
I'm trying to determine if the relationship between Free Ammonia and Total
Ammonia is linear or exponential based on a change in pH, and if there are
other factors (e.g. water temperature, etc.) that affect the equation.

Would lowering the pH be a faster measure to reduce free ammonia in a tank,
compared to doing a partial water change?

[IDzine01]

I'm certain that temperature plays a role. The warmer the water the
more toxic ammonia becomes present.

here's a link I found when doing a quick search:
http://www.thekrib.com/Chemistry/ammonia-toxicity.html

Lowering the pH may or may not be faster, but it has more severe
consequences to the fish. It's much safer to keep the pH stable and
dilute the ammonia/water then to drop the pH. Remember that pH is
measured logarithmicly so what may seem to be a small change to you is
a big one for the fish.

For example: a pH of 6.0 is ten times more acidic then a pH of 7.0 and
a pH of 5.0 is then 100 times more acidic then that 7.0 pH level.

[Elaine T]

Gfishery wrote:
> FA = Free Ammonia, TA = Total Ammonia
>
> My humble attempt at understanding their relationship:
> (am I even close?)
>
> FA = 0 for pH < 7, (Free Ammonia can't exist under ph 7 ?)
> FA = k*(ph-7)*TA , where 0 < k < 1 , and current pH > 7
>
> If Free Ammonia depends on temperature as well, I suppose the formula
> will be much more complicated.
>
You're close, but it apparantly depends on both temperature and
salinity. Also equilibrium constants are not limited to the range of 0
to 1 and pH is typically expressed as the concentration of hydrogen
ions. I'm going to use standard chemical notation of [] to indicate
concentration and K to indicate the equilibrium constant for the
reaction. So...

K = [NH3][H+]/[NH4+]

The following reference gives a temperature and salinity dependent
version of K.

www.geo.uu.nl/Research/Geochemistry/kb/Knowledgebook/NH4_dissociation.pdf

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><

[Elaine T]

Gfishery wrote:
> "IDzine01" > wrote in message
> oups.com...
>
>>There's a chemical reaction taking place.
>>
>>In acidic water ammonia ions (NH3) react with water to create ammonium
>>ions (NH4+) and hydroxyl ions (OH-). When water is alkaline the
>>reaction goes the opposite way because, as there is already an
>>abundance of hydroxyl ions present in alkaline water. Instead of
>>creating ammonium (NH4+) out of ammonia (NH3) and water (H2O) they
>>hydroxyl ions (OH-) split from ammonium (NH4+) to create ammonia (NH3)
>>and water (H2O).
>>
>>Did I confuse you? I confused me.
>
>
> No, not totally. I have a fairly limited chemistry/biology background.
> I'm trying to determine if the relationship between Free Ammonia and Total
> Ammonia is linear or exponential based on a change in pH, and if there are
> other factors (e.g. water temperature, etc.) that affect the equation.
>
> Would lowering the pH be a faster measure to reduce free ammonia in a tank,
> compared to doing a partial water change?
>
>
Lowering pH will reduce the amount of free ammonia far faster than a
water change. A 50% water change only lowers it by half and often
raises tank pH as well. Dropping the pH can reduce it by 10-fold very
rapidly.

In practice, I haven't changed the pH of a tank with ammonia in it for
years. I rely on ammonia detoxifying chemicals like AmQuel if I make a
mistake and have ammonia in a tank. They work fast and I've never seen
any toxic effects from them on plants, fish, or inverts.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><

[Gfishery]

"Elaine T" > wrote in message
. ..
> Gfishery wrote:
> > "IDzine01" > wrote in message
> > oups.com...
> >
> >>There's a chemical reaction taking place.
> >>
> >>In acidic water ammonia ions (NH3) react with water to create ammonium
> >>ions (NH4+) and hydroxyl ions (OH-). When water is alkaline the
> >>reaction goes the opposite way because, as there is already an
> >>abundance of hydroxyl ions present in alkaline water. Instead of
> >>creating ammonium (NH4+) out of ammonia (NH3) and water (H2O) they
> >>hydroxyl ions (OH-) split from ammonium (NH4+) to create ammonia (NH3)
> >>and water (H2O).
> >>
> >>Did I confuse you? I confused me.
> >
> >
> > No, not totally. I have a fairly limited chemistry/biology background.
> > I'm trying to determine if the relationship between Free Ammonia and
Total
> > Ammonia is linear or exponential based on a change in pH, and if there
are
> > other factors (e.g. water temperature, etc.) that affect the equation.
> >
> > Would lowering the pH be a faster measure to reduce free ammonia in a
tank,
> > compared to doing a partial water change?
> >
> >
> Lowering pH will reduce the amount of free ammonia far faster than a
> water change. A 50% water change only lowers it by half and often
> raises tank pH as well. Dropping the pH can reduce it by 10-fold very
> rapidly.
>
> In practice, I haven't changed the pH of a tank with ammonia in it for
> years. I rely on ammonia detoxifying chemicals like AmQuel if I make a
> mistake and have ammonia in a tank. They work fast and I've never seen
> any toxic effects from them on plants, fish, or inverts.

Thanks for all the great info, IDzine01 and Elaine!

And is the amount of Nitrosomonas that grow in a tank triggered by and
dependent on
the free ammonia or the total ammonia?

[Elaine T]

Gfishery wrote:
> "Elaine T" > wrote in message
> . ..
>
>>Gfishery wrote:
>>
>>>"IDzine01" > wrote in message
oups.com...
>>>
>>>
>>>>There's a chemical reaction taking place.
>>>>
>>>>In acidic water ammonia ions (NH3) react with water to create ammonium
>>>>ions (NH4+) and hydroxyl ions (OH-). When water is alkaline the
>>>>reaction goes the opposite way because, as there is already an
>>>>abundance of hydroxyl ions present in alkaline water. Instead of
>>>>creating ammonium (NH4+) out of ammonia (NH3) and water (H2O) they
>>>>hydroxyl ions (OH-) split from ammonium (NH4+) to create ammonia (NH3)
>>>>and water (H2O).
>>>>
>>>>Did I confuse you? I confused me.
>>>
>>>
>>>No, not totally. I have a fairly limited chemistry/biology background.
>>>I'm trying to determine if the relationship between Free Ammonia and
>
> Total
>
>>>Ammonia is linear or exponential based on a change in pH, and if there
>
> are
>
>>>other factors (e.g. water temperature, etc.) that affect the equation.
>>>
>>>Would lowering the pH be a faster measure to reduce free ammonia in a
>
> tank,
>
>>>compared to doing a partial water change?
>>>
>>>
>>
>>Lowering pH will reduce the amount of free ammonia far faster than a
>>water change. A 50% water change only lowers it by half and often
>>raises tank pH as well. Dropping the pH can reduce it by 10-fold very
>>rapidly.
>>
>>In practice, I haven't changed the pH of a tank with ammonia in it for
>>years. I rely on ammonia detoxifying chemicals like AmQuel if I make a
>>mistake and have ammonia in a tank. They work fast and I've never seen
>>any toxic effects from them on plants, fish, or inverts.
>
>
> Thanks for all the great info, IDzine01 and Elaine!
>
> And is the amount of Nitrosomonas that grow in a tank triggered by and
> dependent on
> the free ammonia or the total ammonia?
>
First the sum of NH3 + NH4+ is "free ammonia." It's measured on a
salicylate test kit.

"Total ammonia" is NH3 + NH4+ + ammonia bound to detoxifiers. It's
measured on a Nesslers test.

Nitrosomonas obviously grows on free ammonia, and the more in the tank,
the more "food" they have (within reason, of course). As for total
ammonia, Kordon claims that Nitrosomonas and plants can both use AmQuel
bound ammonia. This means that total ammonia can trigger Nitrosomonas
as well. 1 ppm total ammonia is plenty adequate to get Nitrosomonas
growing.

So you know, I have heard of folks having trouble cycling tanks with
some of the ammonia detoxifiers. I've personally never had trouble
cycling a tank using plain AmQuel.

Disclaimer: I have no personal connection with Kordon. I just like
their product so have done some research on it and am to lazy to test
anything else.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><
rec.aquaria.* FAQ http://faq.thekrib.com

[David C. Stone]

In article >, Elaine T
> wrote:

[snip]
> >
> First the sum of NH3 + NH4+ is "free ammonia." It's measured on a
> salicylate test kit.
>
> "Total ammonia" is NH3 + NH4+ + ammonia bound to detoxifiers. It's
> measured on a Nesslers test.
>
> Nitrosomonas obviously grows on free ammonia, and the more in the tank,
> the more "food" they have (within reason, of course). As for total
> ammonia, Kordon claims that Nitrosomonas and plants can both use AmQuel
> bound ammonia. This means that total ammonia can trigger Nitrosomonas
> as well. 1 ppm total ammonia is plenty adequate to get Nitrosomonas
> growing.

And to add to the plethora of information:

I don't know whether the Nitrosomonas consume the NH3 of the NH4+, but
it doesn't really matter; because the are in equilibrium, consumption of
one will result in conversion of the other form to restore the
equilibrium balance between the two.

Oh, and to respond to the initial question, the relationship between
pH and the amount of NH3 versus NH4+ is not linear, it's sigmoidal
(i.e. an S-shaped curve), The "turning point" depends on the type of
acid you try and adjust the pH with, so probably won't be at pH 7.
If you're curious, look up pH or acid-base titrations in a general
chemistry text and, more specifically, weak acid-strong base and
weak acid-weak base.