# [Wet Thumb Forum]-NitrAte



## DataGuru (Mar 11, 2005)

I was just wondering.
In a natural planted tank, would you have less nitrAte formed than in a tank with the same bioload and plant mass that had filtration going?

Since the plants would be doing more of the work, they'd be using more ammonia than in a filtered tank. ??


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## DataGuru (Mar 11, 2005)

I was just wondering.
In a natural planted tank, would you have less nitrAte formed than in a tank with the same bioload and plant mass that had filtration going?

Since the plants would be doing more of the work, they'd be using more ammonia than in a filtered tank. ??


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## dwalstad (Apr 14, 2006)

Dear Betty,

I would predict that planted tanks with heavy biological filtration would have more nitrates than those with less biological filtration. However, it remains to be tested.

Nitrifying bacteria and plants compete for ammonia. If filter bacteria get the ammonia, then plants are forced to use nitrates. Because nitrate uptake requires energy, plants will take up less nitrogen from the ecosystem if it given to them as nitrates. Ammonia, on the other hand, easily enters the plant and may accumulate in excess (about 2 to 3 fold) of the plant's N requirements.

I have yet to see any need for biological filtration in my planted aquariums.


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## DataGuru (Mar 11, 2005)

Cool. That's what I was thinking.

It seems like I remember that 1ppm ammonia gets converted to ~4 ppm nitrAte by the biobugs, so it would make sense that if the plants got to the ammonia first, there'd be less nitrAte produced.


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## dwalstad (Apr 14, 2006)

I'm sorry, but the nitrification reaction is a one-to-one conversion of ammonia to nitrate. For every ammonia-N processed by nitrifying bacteria, one nitrate-N is produced. See reactions for nitrification on page 63 of my book.

Aquatic plants take up more N if it is ammonia than if it is nitrate. What nitrogen plants need to survive and what they actually accumulate ("luxury accumulation") differs. For example, the minimal N content of aquatic plants is about 1%. This is the "critical concentration" of N cpntent for aquatic plants. However, aquatic plants are found with an N concentration of 2 to 4%. This is the nitrogen excess that they will accumulate in excess of what they actually need. Ammonia (in contrast to nitrates) easily and uncontrollably enters plants. 

Thus, an aquarium plant in the presence of ammonia may accumulate more nitrogen than one presented with nitrogen in the form of nitrates.


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## DataGuru (Mar 11, 2005)

So is this version correct:

1 ammonia molecule (NH4+) plus 2 water molecules (H2O) 
yields 
1 nitrIte molecule (NO2-) and 8 hydrogen ions (H+) 

The nitrIte molecule (NO2-) combines with 1 water molecule (H2O) 
and yields 
1 nitrAte molecule (NO3-) and 2 hydrogen ions (H+) 

That looks one to one to me. not one to four.

Those 10 hydrogen ions released from converting each ammonia molecule to nitrAte are what eventually drops pH. Wow.


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## dwalstad (Apr 14, 2006)

The overall nitrification reaction (p. 63 my book) only releases two protons (H+s), not 10. 

Depending on the water alkalinity's and other factors, this acid release can bring the pH down. 

Tanks with no plants and heavy biological filtration often will show a pH decline.


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## Slippery Fingers (Mar 19, 2003)

> quote:
> 
> Originally posted by Betty:
> Cool. That's what I was thinking.
> ...


Both correct and wrong...

1 ion of NH4+ to 1 ion of NO3- is equivalent to 1 molecular weight of NH3+ to 3.44 molecular weight of NO3-

Therefore 1ppm(mg/L) of NH4+ will convert to 3.44ppm(mg/L) of NO3-.

However, that is not the reason why the plants got to ammonia first.

BC


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## DataGuru (Mar 11, 2005)

That's what I remember reading that I haven't been able to find again. It was molecular weight.

What's not the reason the plants get to ammonia first?


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## imported_Creature (Feb 6, 2003)

Just wanted to add, that we should be using the correct term "ammonium" for NH4+. Plants utilize ammonium or nitrate as stated earlier.


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## dwalstad (Apr 14, 2006)

I was just wondering.
In a natural planted tank, would you have less nitrAte formed than in a tank with the same bioload and plant mass that had filtration going?

1 ion of NH4+ to 1 ion of NO3- is equivalent to 1 molecular weight of NH3+ to 3.44 molecular weight of NO3-

Therefore 1ppm(mg/L) of NH4+ will convert to 3.44ppm(mg/L) of NO3-.

**This conversion is correct. However, when I talked earlier about plants taking up "more", I meant more nitrogen (N). The fact that the nitrate molecule weighs about 3.4 times more than the ammonia molecule is (in my opinion) less relevant to this discussion.

However, let's not forget about soil bacteria. Under anaerobic conditions, they will be converting nitrate to nitrogen gases that will escape from the tank. Also, ammonia gas will escape from the water directly into the air. (That's why fish sealed in plastic shipping bags have such a tough time; much of the ammonia gas stays within the bag keeping water ammonia levels high.) 

Therefore, plants and biological filtration only partially control nitrate and ammonia levels. My tanks may have wildly different nitrate readings, varying from 2 to 80 ppm.


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## Tyrone Genade (Jan 1, 2005)

The conversion of ammonia (NH_3) to nitrate (NO_3-1) via nitrite uses oxygen not water. Water is a byproduct of the process. The exact reactions differ from bacteria to bacteria. See here. This is perhaps a bit more complicated than one may need for explanation however. This  may be more "simple".

Because most tanks' pH tend to be below 9 ammonia exists mainly as ammonium (NH_4+) so one would have to add another proton coming loose in the above equations. Because plants maintain a negative electrochemical potential accross their cell walls (i.e. they have a higher concentration of positively charges molecules outside rather than in the cells) the NH_3+ is able to enter the cells without the need for active transport whereas NO_3- has to be pumped accross against the gradient. I am unfortunatly unable to find a nice link to explain this. :-( So we will have to rely on what I can recall from my plant physiology courses.

By the way, the plant maintains this gradient not to import ammonium but to import calcium, magnesium, potassium etc... The latter salts generally occur as insoluble precipitates. The plants pump H+ out of their stems to lower the pH around themselves. The low pH dissolves the salts. This is also why UG filters are not good as they clear the H+ excess away starving the plant of needed minerals.

I think I have now wondered off topic abit...

tt4n


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## Maurici (May 31, 2004)

Is clear that the explanations given by Tyrone to some of the points are very illustrative. You also post:


> quote:
> 
> the NH_3+ is able to enter the cells without the need for active transport whereas NO_3- has to be pumped accross against the gradient.


I've read that NO3- and NH4+ need a co-transport of protons by the I mechanism (in Epstein terminology)related to differences of intra vs. extracellular pH.
Other information I've found is related to terrestrial plants (like wheat) but can be useful to understand uses of different sources of N in most of our (non natural







)tanks (yes, perhaps it would be better to post it on the other plant forum). As an abstract it talk about *CO2 inhibition of shoot NO3- assimilation which would contribute to the response of natural ecosystems to rising CO2 levels. Plants vary in their relative dependence upon NH4+ and NO3- as nitrogen sources (Bloom, 1997) and in their balance between shoot and root NO3- assimilation (Andrews, 1986). Their results suggest that rising atmospheric CO2 will favor taxa that prefer NH4+ as a nitrogen source or assimilate NO3- primarily in their roots.* I've used its own words (slighty modified) and note that the references refer to bibliography there reported.


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