# Urea CO(NH2)2



## Edward (Apr 11, 2005)

Urea based aquatic plant fertilizing is becoming more popular lately while not having enough supporting information. I have added this page describing urea recipes, calculations, ratios and other necessities.

Please feel free to add any comments you have about using urea fertilizers.

Thank you
Edward


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## happi (Dec 18, 2009)

Thanks Edward, it will help people understand about Urea dosing, am sure people will also like the results and benefits of using it.


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## citrusvrucht (Mar 1, 2016)

Nice write up! 

One thing though, algae can use urea through the urease enzyme, some even use ATP-urea amidolyase.
Adding small quantity's of nickel could also be beneficial because it is needed for urease. Be VERY careful with nickel, it is highly toxic! Safest way is to buy or let a specialist make a 1M solution.


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## WaterLife (Jul 1, 2015)

Nice Ed!

Any sources to get Urea (powder form?)? CO(NH2)2

I am a complete newbie to plant fertilization/chemistry, so please bear with me.
I just had a brief look over the linked site, and if I am understanding it correctly, Urea only provides Carbon and Nitrogen for the plants. Correct?
Is that form of Carbon in a usable form for the plants? (looks like the formula shows it as CO2 - Carbon Dioxide, but just want to verify)

Now, how about the urea in our urine? No?  Pretty sure there are plenty of toxins in there that would kill fish and potentially harm plants (can fishless cycle a tank though).


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## Nordic (Nov 11, 2003)

People use to pee in their tanks to help it cycle faster...


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## happi (Dec 18, 2009)

citrusvrucht said:


> Nice write up!
> 
> One thing though, algae can use urea through the urease enzyme, some even use ATP-urea amidolyase.
> Adding small quantity's of nickel could also be beneficial because it is needed for urease. Be VERY careful with nickel, it is highly toxic! Safest way is to buy or let a specialist make a 1M solution.


yeh i use Nickel in my Urea solution, i dose anywhere between 0.00001 to 0.0001 ppm Ni daily, not sure what are the safe doses for Ni.


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## Edward (Apr 11, 2005)

happi said:


> yeh i use Nickel in my Urea solution, i dose anywhere between 0.00001 to 0.0001 ppm Ni daily, not sure what are the safe doses for Ni.


 Thank you happi,
Do you see a difference when dosing nickel? Why the range, makes a difference too?

Thank you WaterLife,
Urea provides fast nitrogen and some carbon to plants. It is available in farmers supply stores.

Thank you citrusvrucht,
I fixed the algae info.
We need to supply nickel so plants can make Urease enzyme? One reason why trace element mixes don’t have nickel is that there is plenty of it naturally in tap waters, they say. And, yes some literature has nickel listed as essential micronutrient. 


Ok, so plants need nickel to make enzyme Urease to catalyze the hydrolysis of urea into carbon dioxide and ammonia. I was looking for a fast solution and … I dosed one coin per 25 gallon or 100L. What do you think?


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## mistergreen (Dec 9, 2006)

You can buy a bag of urea on amazon or e bay.

I have a feeling a nickel coin isn't going to do much in adding nickel into the water column. You'd need soluble nickel ions like iron ions for plants. Check your microferts for nickel.


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## WaterLife (Jul 1, 2015)

By the way, US nickels are actually composed of 75% copper and only 25% nickel. I don't know about European or Canadian coins.


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## mistergreen (Dec 9, 2006)

WaterLife said:


> By the way, US nickels are actually composed of 75% copper and only 25% nickel. I don't know about European or Canadian coins.


It's more expensive to make coins these days than their worth 
Soon, it'll be all zinc and tin.


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## happi (Dec 18, 2009)

Edward said:


> Thank you happi,
> Do you see a difference when dosing nickel? Why the range, makes a difference too?



its one of those nutrients which are present in our tap water, but i use 100% RO water, so adding little Ni should help, but there is no way to tell if its working or not, its not like NPK, Fe deficiency which can be spotted easily. 

i have read Kekon post on nickel and i love this guys posts, his posts have some good info, here are some quotes from his posts regarding nickel and cobalt, i did not add cobalt in my mix for this same reason.

*Kekon: I've just purchased some NiCl2 and begun to dose. I dose 0.00074 ppm Ni daily. As far as i know in natural waters (freshwaters) nickel levels are in range 0.002..0.010 ppm. In rivers of Western Europe it is 0.075 ppm. As far as i know colbalt is needed only by one aquatic plant - Azolla. I also have some CoCl2 * 6H2O (as a source of cobalt) and KI (as a source of iodine). If adding nickel doesn't give any positive results i will try with iodine and cobalt.*

another thread by him:
How my own micro & macro ferts work - General Aquarium Plants Discussions - Aquatic Plant Central


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## nilocg (Jul 12, 2010)

I just did some reading around and most all commercial liquid fertilizer companies who sell a nitrogen supplement meant for freshwater plants use urea.

Seachem says the following about their flourish nitrogen product in the FAQ section: 


Q: It says on your label that Flourish Nitrogen provides nitrogen in both the nitrate form and the ammonium form. Isn't ammonia bad?

A: Ammonium and ammonia are not the same thing. No free ammonia is released because the ammonium in Flourish Nitrogen is complexed and unavailable until utilized by the plants.


While my chemistry background isnt as good as some of yours here, isnt this statement a little of a half truth? Clearly there are a lot of people out there that have used one of the commercial products with urea in a tank with a higher ph. How big of a deal is this?


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## jw.cS (Jan 13, 2005)

I don't have anything to add to the discussion but I have a question. Would it be feasible to dose urea exclusively as the nitrogen source?

I know this is a loaded question that pertains to ambient water column nitrogen concentration, among others. But assuming that I have chronic 0-5 ppm NO3 water column level (which I do...for shrimps and too lazy for test kits or whatnot), is it ok to rely on dosing urea for the plants at a rate of 1 ppm Urea (2.0649 ppm NO3 equivalent) every two days or whatever? My pH is in the low 6.

I figure, at worst, if no urea is consumed by the plants, then I will end up with no more than ~25 ppm NO3 over time, assuming 3x/week 1 ppm Urea dosages and 25% weekly water changes.

Will you offer some feedback?


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## happi (Dec 18, 2009)

nilocg said:


> I just did some reading around and most all commercial liquid fertilizer companies who sell a nitrogen supplement meant for freshwater plants use urea.
> 
> Seachem says the following about their flourish nitrogen product in the FAQ section:
> 
> ...


i used seachem nitrogen in my hard water tank before without any issue, the NH4 is very little in seachem which plant will uptake very quickly, while urea release NH4 into the plant directly and very slowly, while some of it convert into NO3 if you are overdosing it. NO3 content is very low in seachem and aqua vitro compare to Urea, in aqua vitro line 25% is NO3, 25% Nh4 and 50% is Urea.

there is nothing new about why most of the top brand use NH4 and Urea in there nitrogen, they been around forever now.

i would stick with Urea and NO3 mix just to be safe.


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## nilocg (Jul 12, 2010)

happi said:


> i used seachem nitrogen in my hard water tank before without any issue, the NH4 is very little in seachem which plant will uptake very quickly, while urea release NH4 into the plant directly and very slowly, while some of it convert into NO3 if you are overdosing it. NO3 content is very low in seachem and aqua vitro compare to Urea, in aqua vitro line 25% is NO3, 25% Nh4 and 50% is Urea.
> 
> there is nothing new about why most of the top brand use NH4 and Urea in there nitrogen, they been around forever now.
> 
> i would stick with Urea and NO3 mix just to be safe.


So how many ppm urea do you feel safe dosing in higher ph tanks?


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## Nordic (Nov 11, 2003)

Urinary excretion is the major route for the elimination of absorbed nickel... I.e. as long as we have nickel in our diet, we pee nickel.
Looks like the old folks had it right.


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## jw.cS (Jan 13, 2005)

happi said:


> urea release NH4 into the plant directly and very slowly


Forgive my ignorance, does this mean that plants and bacteria take up the entire urea molecule and extract the NH4 internally or the urea molecule dissolves into NH4 and CO2 in the water column and those ions are individually picked up by the plants and animals? If the latter, then is the urea crystal very hard to dissolve in solution? Is this what you mean by "urea release NH4 into the plant directly and *very slowly*" (emphasis is mine)?

Thank you for your clarification.


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## nilocg (Jul 12, 2010)

Nordic said:


> Urinary excretion is the major route for the elimination of absorbed nickel... I.e. as long as we have nickel in our diet, we pee nickel.
> Looks like the old folks had it right.


Still doesnt make it a good idea to urinate into your tank, you excrete more than just urea and nickel.


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## Nordic (Nov 11, 2003)

I bet, my fish would just keel over. Mosquitos fly right past me and bite my wife.


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## nilocg (Jul 12, 2010)

Nordic said:


> I bet, my fish would just keel over. Mosquitos fly right past me and bite my wife.



Haha, same with me.


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## happi (Dec 18, 2009)

jw.cS said:


> Forgive my ignorance, does this mean that plants and bacteria take up the entire urea molecule and extract the NH4 internally or the urea molecule dissolves into NH4 and CO2 in the water column and those ions are individually picked up by the plants and animals? If the latter, then is the urea crystal very hard to dissolve in solution? Is this what you mean by "urea release NH4 into the plant directly and *very slowly*" (emphasis is mine)?
> 
> Thank you for your clarification.


far as i remember plant will uptake the co2 and urea directly, including bacteria, however plant cannot store it, that is why you dont want to overdose it. Nh4 from NH4no3 will be directly floating around in the water until plant absorb it quickly enough, that is the reason you should not dose too much NH4No3, urea can be dosed in higher doses without issue. 

i could be wrong but this is what i have observed and read so far.


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## Edward (Apr 11, 2005)

http://www.who.int/water_sanitation_health/gdwqrevision/nickel2005.pdf

Nickel in Drinking water


1.4 Environmental fate

Nickel occurs predominantly as the ion Ni(H2O)6 2+ in natural waters at pH 5–9 (IPCS, 1991). Complexes with ligands, such as OH-, SO4 2-, HCO3-, Cl-, and NH3, are formed to a minor degree in this pH range.


2.2 Water
Nickel concentrations in groundwater depend on the soil use, pH, and depth of sampling. The average concentration in groundwater in the Netherlands ranges from
7.9 μg/litre (urban areas) to 16.6 μg/litre (rural areas). Acid rain increases the mobility of nickel in the soil and thus might increase nickel concentrations in groundwater (IPCS, 1991). In groundwater with a pH below 6.2, nickel concentrations up to 980 μg/litre have been measured (RIVM, 1994).

In Canada, the median nickel level in drinking-water supplies was below the detection limit of 2 μg/litre; the maximum level observed was 69 μg/litre (Méranger et al.,
1981). In drinking-water in the USA, 90% of all samples (n = 2503) contained ≤10 μg/litre, and 97% had nickel concentrations of ≤20 μg/litre (ATSDR, 1996).

In Europe, reported nickel concentrations in drinking-water were generally below 10 μg/litre (IPCS, 1991). Nickel levels below 1 μg/litre have been reported from
Denmark and Finland (Punsar et al., 1975; Gammelgaard & Andersen, 1985). Average dissolved nickel concentrations in surface water in the rivers Rhine and
Meuse are below 7 μg/litre (RIWA, 1994).

Increased nickel concentrations in groundwater and municipal tap water (100–2500 μg/litre) in polluted areas and areas in which natural nickel was mobilized have been
reported (McNeely et al., 1972; Hopfer et al., 1989). Water left standing overnight in plumbing fittings plated with chromium on a base of nickel contained a nickel
concentration of 490 μg/litre (Andersen et al., 1983).

Certain stainless steel well materials were identified as the source of increased nickel concentrations in groundwater wells in Arizona, USA. Mean nickel levels were 8–395 μg/litre; in some cases, nickel levels were in the range 1–5 mg/litre (Oakley & Korte, 1996).

Leaching of nickel from chromium–nickel stainless steel pipework into drinkingwater diminished after a few weeks; as chromium was rarely found at any time in the
water, this indicates that the leakage of nickel is not of corrosive origin, but rather attributable to passive leaching of nickel ions from the surface of the pipes (Schwenk, 1992). Concentrations of nickel leaching from new stainless steel pipes used for drinking-water were up to 6 μg/litre (Nickel Development Institute, personal
communication, 2004). This maximum concentration can be increased when the pipes are assembled with tinned copper and gunmetal fittings. Fittings such as taps, which
are chromium-plated, release much higher concentrations, but these decrease significantly with time (EU, 2004).

Concentrations of nickel in water boiled in electric kettles may, depending on the material of the heating element, be markedly increased, especially in the case of new or newly decalcified kettles. The greatest concentrations are associated with nickelplated elements; however, leaching decreases over time. Nickel concentrations in the range 100–400 μg/litre, with extreme values over 1000 μg/litre, have been reported (Rasmussén, 1983; Pedersén & Petersén, 1995; Berg et al., 2000; United Kingdom Drinking Water Inspectorate, 2002; EU, 2004).

Nickel concentrations in bottled mineral water will depend on the source and any treatment applied. Levels of nickel in a selection of bottled mineral waters were below the detection limit of 25 μg/litre (Allen et al., 1989).


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## WaterLife (Jul 1, 2015)

nilocg said:


> I just did some reading around and most all commercial liquid fertilizer companies who sell a nitrogen supplement meant for freshwater plants use urea.
> 
> Seachem says the following about their flourish nitrogen product in the FAQ section:
> 
> ...


Yeah, I've always thought the same about substrates that people say they only leach out ammonium.

Unless there is something that can lock ammonium in it's ammonium form regardless of pH that I don't know about?


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## Edward (Apr 11, 2005)

jw.cS said:


> I don't have anything to add to the discussion but I have a question. Would it be feasible to dose urea exclusively as the nitrogen source?
> 
> I know this is a loaded question that pertains to ambient water column nitrogen concentration, among others. But assuming that I have chronic 0-5 ppm NO3 water column level (which I do...for shrimps and too lazy for test kits or whatnot), is it ok to rely on dosing urea for the plants at a rate of 1 ppm Urea (2.0649 ppm NO3 equivalent) every two days or whatever? My pH is in the low 6.
> 
> ...


 The problem with this is that urea breaks down in hours. So if you dose 2 ppm of urea (2 ppm as NO3) every other day then clearly, plants will have the urea in its original form only on dosing days. On the no dosing days plants will have NO3. Any unused form of N will eventually accumulate as NO3.

The 25% weekly water changes may or may not be adequate. Your best strategy would be daily dosing before lights go on while monitoring the NO3 and other compound accumulation.


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## mistergreen (Dec 9, 2006)

hmm, so urea can't be in a solution for dosing since it breaks down?


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## Edward (Apr 11, 2005)

Main mode of degradation is enzymatic mineralization. In soil and water urea is expected to biodegrade fairly rapidly to ammonia and bicarbonate. Main mode of degradation : 1) NH2CONH2 + 2H20 (Urease-enzyme) --> NH3 + NH4 + HCO3- 2) NH4+ + 1.5 O2 Nitrosomonas ---> NO2- + H2O + 2H+ ---> NO2- + 0.5 O2 Nitrobacter ---> NO3

http://www.inchem.org/documents/sids/sids/57136.pdf


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## mistergreen (Dec 9, 2006)

It would've been a perfect fert for peristaltic auto dosing. I guess in dry form is best.


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## bcarl_10gal (Feb 13, 2014)

Great thread. Anyone start using a little Urea in their Macro bottle with KNO3 and want to share their recipe and observations?


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## Edward (Apr 11, 2005)

bcarl_10gal said:


> Great thread. Anyone start using a little Urea in their Macro bottle with KNO3 and want to share their recipe and observations?


 What is missing here?


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## bcarl_10gal (Feb 13, 2014)

Edward said:


> What is missing here?


It considers the dose of Urea independently from KNO3 unless I am reading it wrong and you dose the Macros Bottle with the Urea bottle daily. And even then some would argue to scale up the macro's a bit to reach EI levels.


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## Edward (Apr 11, 2005)

bcarl_10gal said:


> And even then some would argue to scale up the macro's a bit to reach EI levels.


 You can dose as much as you want.



bcarl_10gal said:


> It considers the dose of Urea independently from KNO3 unless I am reading it wrong and you dose the Macros Bottle with the Urea bottle daily.


 Unused urea will end up as NO3 so I don’t see the point in dosing KNO3 with it. As for the K portion I made the recipe as a direct KNO3 replacement. That way the N - K balance is maintained. This makes it easy to switch back and forth between KNO3 and urea fertilizing.


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## jw.cS (Jan 13, 2005)

Edward said:


> Main mode of degradation is enzymatic mineralization. In soil and water urea is expected to biodegrade fairly rapidly to ammonia and bicarbonate. Main mode of degradation : 1) NH2CONH2 + 2H20 (Urease-enzyme) --> NH3 + NH4 + HCO3- 2) NH4+ + 1.5 O2 Nitrosomonas ---> NO2- + H2O + 2H+ ---> NO2- + 0.5 O2 Nitrobacter ---> NO3
> 
> http://www.inchem.org/documents/sids/sids/57136.pdf


From what is given, is it correct to assume that urea can only be broken down into its constituents internally by plants and animals since enzymes are required? Please refresh my chemistry. If that were the case, then what form does urea exist as in solution since it does in fact *dissolve*? The reason I ask this is because according to the referenced PDF, 98% of the urea will be degraded within 24 hours. Whether this is due to biological action or spontaneous decomposition, how stable is a solution of urea? Everything I have read thus far (admittedly not a lot) indicates that urea should be prepared *fresh**. What time frame does "fresh" refer to is unclear. Would it make sense to dose dry instead?

_*"Urea solutions should always be freshly prepared and used, as solutions of urea may develop a significant concentration of reactive cyanate ions upon standing." (Sigma)_



Edward said:


> The problem with this is that urea breaks down in hours. So if you dose 2 ppm of urea (2 ppm as NO3) every other day then clearly, plants will have the urea in its original form only on dosing days. On the no dosing days plants will have NO3. Any unused form of N will eventually accumulate as NO3.
> 
> The 25% weekly water changes may or may not be adequate. Your best strategy would be daily dosing before lights go on while monitoring the NO3 and other compound accumulation.


This is 50% why I want to dose every 2 days because for my aquarium size, measuring anything less than 1/64 tsp is a bit uhmmmm difficult. The other part is I am a bit lazy and do not want daily dosing.  Any unused urea will be converted into NO3, which the plants can take up anyway--so no real loss or problem right? If there's no lobster then eat the dang potato. You're not going hungry.

As far as accumulation goes, assuming zero uptake, my math is as follows...and please do check my math:

1 ppm urea every 2 days => ~ 2 ppm NO3
After week 1, 2 x 3 = 6 ppm NO3
After 25% water change, 6 - (0.25 x 6) = 4.5 ppm NO3
After week 2, 4.5 + 6 ppm NO3 = 10.5 ppm NO3
After 25% water change, 10.5 - (0.25 x 10.5) = 7.875 ppm NO3

Do that a bunch of times and the accumulation should mathmatically work out to be 4 times the weekly dosage: 4 x 6 = 24 ppm NO3.

The total amount of NO3 in the tank should not exceed this number. Is this correct?

---

Now this is an aside--perhaps off topic. Concerning water column nitrogen level for a planted tank, there is an obvious difference between one where there is a persistent 1 ppm NO3 and one with persistent 30 ppm NO3. Why is this? Is it because at the former dilution, the plants have a harder time scavenging for the nitrogen source since those nitrogenous ions aren't coming into contact with the leaves as much? Is this why EI levels result in more robust plant growth?

I ask because in my system where I have to balance sensitive shrimps, plants and my general laziness, my nitrate level always hover 0-5 ppm. So is the addition of 1 ppm urea (2 ppm NO3 equivalent) sufficient to keep plants growing while maintaining low maximum NO3 levels without me having to freak out and test kits this tank to death?

My need for experimentation and my fear of killing these stupid shrimps aren't compatible at times.


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## Edward (Apr 11, 2005)

happi said:


> yeh i use Nickel in my Urea solution, i dose anywhere between 0.00001 to 0.0001 ppm Ni daily, not sure what are the safe doses for Ni.


_
“In Canada, the median nickel level in drinking-water supplies was below the detection limit of 2 μg/litre; the maximum level observed was 69 μg/litre (Méranger et al., 1981). In drinking-water in the USA, 90% of all samples (n = 2503) contained ≤10 μg/litre, and 97% had nickel concentrations of ≤20 μg/litre (ATSDR, 1996).”_

happi, I am also using 100% RO, and luckily not DI. Here is why. 
The usual low tap water nickel level is as low as a few µg/L, let’s assume 1 µg/L. RO filter strips about 90% minerals, leaving 10% minerals in the product water. So, 1µg/L is 1000ng/L, minus 90% is 100ng/L.

So there is a good chance that even after RO filter we get at least 100ng/L of nickel. Your nickel dose is between 10 – 100 ng/L. If your Ni dose is adequate to support the urease enzyme then we can assume that tap water and RO water will most likely be as well.


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## happi (Dec 18, 2009)

if Urea does degrade into NO3 in the solution, then i don't really see any benefit of using it then, we can simply increase the NO3 by KNO3, but IME urea dosing even from the solution was very beneficial to the plants compare to any other source of nitrogen.

plant that did not grow in KNO3 dosing, actually grew when urea was dosed from the solution, plant also had better fuller growth.


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## mistergreen (Dec 9, 2006)

I'll make sure to add urea to my fertilizer app. I'm curious how long it's stable in distilled water. I'll have to buy a bag and pull out the NO3 & NH3 test kit.


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## Edward (Apr 11, 2005)

Ok, so this is urea.
If you want to try fresh dosing then 1 pellet is 1 ppm as NO3 per 10 gallon or 40L. 
Dissolve first!


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## happi (Dec 18, 2009)

Edward said:


> Ok, so this is urea.
> If you want to try fresh dosing then 1 pellet is 1 ppm as NO3 per 10 gallon or 40L.
> Dissolve first!


can you tell me how many gram 1 urea pellet is? i have the powdered version of it.

if am correct 0.091 gram urea will add 1 ppm NO3 in 50gallon.


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## Edward (Apr 11, 2005)

happi said:


> can you tell me how many gram 1 urea pellet is? i have the powdered version of it.


 happi, 

19.38 mg of urea is 1 ppm as NO3 per 10 gallon or *40L*

BTW, I have dosed this fresh urea few hours ago and don’t see any difference than the old urea solution.


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## jw.cS (Jan 13, 2005)

Okie dokie. I found the answer to my question.

Given a planted and/or fully cycled tank, 100% of the urea will be biologically processed within 24 hours due to enzymatic actions from the flora/fauna. In an abiotic environment, where (1) the temperature does not approach water's boiling point and (2) the pH stays <7, virtually none of the urea will be hydrolyzed into NH3/4 and CO2.

In effect, we can safely make aqueous solutions of urea with RO/DI water and not worry about degradation under our hobby's operating environment. We can further stabilize the solution by adding an acid (HCl or whatnot) to reduce the pH to ~5, preventing the formation of ammonium cyanate and favoring its equilibrium partner: urea.

Source: Open Chemistry Database and some other MSDS from some company's aqueous urea reagent products that I can't recall. &#55357;&#56833;


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## mistergreen (Dec 9, 2006)

jw.cS said:


> Okie dokie. I found the answer to my question.
> 
> Given a planted and/or fully cycled tank, 100% of the urea will be biologically processed within 24 hours due to enzymatic actions from the flora/fauna. In an abiotic environment, where (1) the temperature does not approach water's boiling point and (2) the pH stays <7, virtually none of the urea will be hydrolyzed into NH3/4 and CO2.
> 
> ...


Awesome, auto dosing this would work great, say 2ppm every few hours safely for the animals.


Sent from my iPad using Tapatalk HD


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## Edward (Apr 11, 2005)

jw.cS said:


> Now this is an aside--perhaps off topic. Concerning water column nitrogen level for a planted tank, there is an obvious difference between one where there is a persistent 1 ppm NO3 and one with persistent 30 ppm NO3. Why is this? Is it because at the former dilution, the plants have a harder time scavenging for the nitrogen source since those nitrogenous ions aren't coming into contact with the leaves as much? Is this why EI levels result in more robust plant growth?


 If moderate nutrient levels are good for ADA then it must be good for me too. I don’t see weak plants in ADA aquariums, or not “robust” enough plants. And I don’t see deformed growth and crazy race against algae.


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## hbosman (Oct 5, 2006)

Since Urea is a good source of nitrogen if, requirements are met, couldn't we just feed the fish more and achieve similar results?


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## Edward (Apr 11, 2005)

hbosman said:


> Since Urea is a good source of nitrogen if, requirements are met, couldn't we just feed the fish more and achieve similar results?


 The thing is fish waste is mostly ammonia, not urea. 
Ammonia is very toxic. Urea is not toxic and comes with carbon as a bonus.


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## mistergreen (Dec 9, 2006)

Edward said:


> The thing is fish waste is mostly ammonia, not urea.
> Ammonia is very toxic. Urea is not toxic and comes with carbon as a bonus.


Doesn't it break down to ammonia? It can be toxic given the right amount and condition.


Sent from my iPad using Tapatalk HD


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## Edward (Apr 11, 2005)

mistergreen said:


> Doesn't it break down to ammonia? It can be toxic given the right amount and condition.


 Only if you overdose and ignore the “What are the necessary prerequisites to use urea safely?”


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## jw.cS (Jan 13, 2005)

*Disclaimer:* I am not an expert in the field, have absolutely no authoritative standing in the community and ugly tanks with dying fish and plants. Please take what is written below with a bottle of brine and learn me. I simply read, do bad math and regurgitate information in an extremely verbose manner.

Always eager to learn so please let me know if I have erred, misrepresented and/or misunderstood the following information and analysis.



mistergreen said:


> Doesn't it break down to ammonia? It can be toxic given the right amount and condition.


*ABSTRACT:* It safe yo!

*ABSTRACT FOR THE INQUISITIVE:* Under our hobby’s operating conditions, urea does not produce the necessary ammonia (NH3) to be detrimental to life or conducive to algae proliferation. This include (1) pH and temperature up to 8.5 and 86 degrees F respectively and/or (2) the completely hydrolization of urea.

*THE WHOLE SHEBANG:*

Although urea does dissolve (very well) in water, it does not degrade into its constituents like NaCl (into Na+ and Cl-) unless acted upon by high temperatures (approaching water’s boiling point) and/or enzymes. This means that a solution of urea + water will still be nonionic urea and water…unlike a solution of table salt (NaCl) + water that breaks into Na+ ions, Cl- ions and water. Edward has shown that urea is quite safe to biological life even at very high concentrations.

However, as soon as dry/aqueous urea is added to an established tank, it is now subjected to biological influences: primarily the enzyme urease and the tank’s pH. Urease is present within plant/animal cells *AS WELL AS* within the water column (including the substrate), either as secreted by the flora/fauna and/or by the decomposition of their rotting corpses. Anywho, whether intracellularly or extracellularly, the urease breaks the urea into ammonia (NH3) and ammonium (NH4) very rapidly.

It is the extracellular portion of the reaction that we worry about (due to NH3) and also where the pH comes into play. We don’t care about the intracellular portion because they exist within the plants/microorganisms themselves so they can’t harm our fishies and inverteBRATS. In a planted tank and/or fully cycled tank, this uptake happens almost instantaneously. But where’s the fun in that? Let’s assume that it doesn’t and urea is being hydrolyzed in solution from some magical source of urease or super tank with boiling water and tanning shrimps—just to see what’ll happen.

In such a system, NH3 and NH4 exist as an equilibrium pair, whose concentrations are primarily determined by pH, where the higher the pH, the more NH3 is available. Again, NH4 is good. NH3 is bad. The pKa of this equilibrium is somewhere at pH 9. So for every degree of pH change, we are talking about a 10 fold change. That means at pH 7 at 77F, the NH3:NH4 ratio is 0.57 to 99.43. That’s hardly any NH3 at all. But again, where’s the freaking fun in that? Let’s just assume we have a pH of 8.5 and temperature of 86 degree F. Why? Cuz I found data for those values. 

At pH 8.5 and 86F, the [NH3] is 20% and the [NH4] is 80% of the total ammonia content. So if I use an API test kit and I measure 100 ppm ammonia, there should be 20 ppm NH3 and 80 ppm NH4. But who the hockey-double-sticks has that much ammonia? Let’s be realistic. Happi, somewhere or another, through personal experimentation, suggests starting at 0.5 ppm urea and maxing out at 2 ppm urea. Since we’re having fun, let’s use 2 ppm urea.

2 ppm urea yields _roughly_ 0.001134 ppm NH3/NH4 according to the stoichiometric relationship in the hydrolysis of urea and subsequent equilibrium yadda yada.

CO(NH2)2 + H2O ->	2 NH3 + CO2
NH3 + H2O <=>	NH4 + OH

0.001134 ppm NH3/NH4 yields _roughly_ 0.000226 ppm NH3 and 0.000907 ppm NH4 according to the aforementioned pKa doohickey. Now, the real question comes in: is 0.000226 ppm NH3 deadly? NO! Not by a long shot. The EPA lists the 1-hour [NH3] LD50 (the point at which 50% of the organism die) as 0.26 ppm and the 4 day [NH3] LD50 as 0.035 ppm. If we were to be overly cautious and scale down the 4-day exposure EPA level by 10 fold to 0.0035 ppm NH3, our level would still be 15 times less: 0.000226 ppm NH3. Assuming all of the resulting ammonical nitrogen exists as NH3, it would still be 3 times LESS than *one tenth* of the LD50 value. Extrapolating Neil Frank‘s comments, “That’s pretty safe. May I have the pizza you promised now?” probably.

In conclusion, even assuming the worst case scenario of (1) very high pH, (2) very high temperature, (3) zero uptake by the flora/fauna and (4) completely hydrolization into NH3, we are still within safe NH3 ranges. At least theoretically. 

---

Happi et al recommends those who dose urea to do so only in pH <7 systems, as extra precaution. He insists further that [urea] exceeding 2 ppm leads to no improved growth and algae blooms.

---

*SOURCES*
Ammonia & Aquaponics Systems
Urea Hydrolysis in Soil Profile Toposequences: Mechanisms Relevant to Nitrogen Transport and Water Quality
Ammonia Toxicity to Freshwater Fish: the effects of pH and temperature
Urea and algae
Perpetual Preservation System: Urea
Happi's Ultimate Fertilizer
Urea
Ammonia
Nitrate (NO3-) versus ammonium (NH4+)

Edward, Happi, Thomas Barr, James et al on various forums, newsletters and things like that. Other places and people that I can’t remember. Apologies to the respective parties from whom everything (and I mean every freaking thing) above was stolen. Please don’t sue.


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## Edward (Apr 11, 2005)

The best write up I have ever read and the funniest!
Thank you jw.cS


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## max88 (Jun 22, 2013)

jw.cS said:


> 2 ppm urea yields _roughly_ 0.001134 ppm NH3/NH4 according to the stoichiometric relationship in the hydrolysis of urea and subsequent equilibrium yadda yada.
> *
> CO(NH2)2 + H2O -> 2 NH3 + CO2*
> NH3 + H2O <=> NH4 + OH


You've completely lost me here! How do I calculate the NH3 equivalent of 2 ppm urea? Am I doing this incorrectly?
CO(NH2)2 = 12+16+(14+1*2)* = 60
NH3 + NH3 = (14+1*3) + (14+1*3) = 34
Assuming all conditions are wrong every bits of urea become NH3
2ppm urea ==>> 2*34/60 = 1.333ppm NH3


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## jw.cS (Jan 13, 2005)

max88 said:


> You've completely lost me here! How do I calculate the NH3 equivalent of 2 ppm urea? Am I doing this incorrectly?
> CO(NH2)2 = 12+16+(14+1*2)* = 60
> NH3 + NH3 = (14+1*3) + (14+1*3) = 34
> Assuming all conditions are wrong every bits of urea become NH3
> 2ppm urea ==>> 2*34/60 = 1.333ppm NH3


You are so right. I have completely neglected to change from g to mg at the end. I bring great shame to my entire ancestral line.










When I get home, I will have to think through this number and the EPA standards. Yay for peer review and the importance of proof reading. :iamwithst


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## max88 (Jun 22, 2013)

:icon_redf Ooops! I didn't mean to say it out loud that it was off by 1,000. I was genuinely confused. Like others have said, that's a great post (and funny).


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## mistergreen (Dec 9, 2006)

darn zeros! We've all been there.


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## Edward (Apr 11, 2005)

One discrepancy at the end of jw.cS’s article doesn’t make the article less valid. He proved his point that urea as prescribed is safe to aquatic life. 

The main focus is on ammonium toxicity which comes from urea. Again, jw.cS proved it is safe when used as prescribed. 

Many companies are using these forms of nitrogen from direct fertilizer additions to ADA Aquasoil substrate. ADA substrates are supplying ammonium to roots and to water column which is not very different from what we are supplying with this liquid fertilizer.


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## happi (Dec 18, 2009)

this week i tested 15 ppm NO3 in single dose from Urea, which is about 4.36 NH4 from Urea, there was a sudden increase in plant growth, fishes and shrimps were fine during this test.


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## Edward (Apr 11, 2005)

happi said:


> this week i tested 15 ppm NO3 in single dose from Urea, which is about 4.36 NH4 from Urea, there was a sudden increase in plant growth, fishes and shrimps were fine during this test.


 Few Q.

biological filtration size
substrate type
tested ppm NH4 ammonium in 24h
tested ppm NO2 nitrite in 24h
tested ppm NO3 nitrate in 24h
% of survivals
plant visual condition


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## happi (Dec 18, 2009)

Edward said:


> Few Q.
> 
> biological filtration size:
> 500+ gph filter with very minimum media, only sponge filter to block debris. i also use 1000gph emersed pump which is hooked to cerges reator, there is no sponge inside the reactor.
> ...


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## mistergreen (Dec 9, 2006)

Po4 is essential in photosynthesis like N and forming oils and carbohydrates. It stimulates blooming and root growth.


Sent from my iPad using Tapatalk HD


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## happi (Dec 18, 2009)

mistergreen said:


> Po4 is essential in photosynthesis like N and forming oils and carbohydrates. It stimulates blooming and root growth.
> 
> 
> Sent from my iPad using Tapatalk HD


yes that is how it works, but there are claims that plant use PO4 mainly from roots and not from water. i was trying to say that if i dont dose the liquid po4 dosing then plant start to slow the growth.


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## Edward (Apr 11, 2005)

happi said:


> i have a feeling that we really dont need to add Ni, most of us should be fine without the need to add Ni, even in 100% RO water i think we can skip the Ni, i personally add it just to make sure that its there in case if its needed, usually urea itself will eventually break down by other bacteria in our tank if i could understand this correctly, from Urea>NH4>NO3.


http://www.tandfonline.com/doi/pdf/10.1080/00380768.1999.10415820
The suitability of urea for the cultivation of field crops has been well documented. Urea is used as the main source of N fertilizer for crops grown in soil (Gould et al. 1986). Its use as N source for crops grown under the hydroponic system has yet to be evaluated. The use of urea in water-culture could be hindered because urea has to undergo hydrolysis with the release of NH4 + which is harmful when absorbed by the plants (Luo et al. 1993). To hydrolyze urea, the enzyme urease requires Ni as a component (Dixon et al. 1975). Urease production in higher plants is strictly controlled by the concentration of Ni and the urease activity of cucumber leaves is markedly suppressed at low Ni concentrations (Watanabe et al. 1994). In species of rye, wheat, soybean, rape, zucchini, and sunflower, Ni is necessary for urea assimilation and thus for the growth of plants on urea-based media (Gerendas and Sattelmacher 1997b).

The requirement of Ni for urea-grown plants has frequently been reported in numerous studies (Polacco 1977; Shimada and Ando 1980; Krogmeier et al. 1991; Gerendas and Sattelmacher 1997a, b). Our results were in agreement with previous findings indicating that the use of 50% urea and 0.05 mg Ni L -I led to a significantly high vegetative growth and minimized the N03 -N and urea-N contents in the spinach shoots. From the results of Exp. 1 we used 0.05 mg Ni L -I for the Ni treated urea solutions in Exp. 2. Maximum vegetative growth (increase of shoot fresh and dry weight) was obtained by the use of a 20% urea solution with Ni addition, which corresponded to the findings of Gerendas and Sattelmacher (1997b).

When plants are grown with a urea nutrient solution, spinach mainly takes-up urea as an intact molecule. To confirm this finding, we analyzed the NH4-N content of the urea solution during the growth period. At that time, no NH4-N was detected.

Urea is seldom used in water culture for several reasons. Firstly, urea can be easily hydrolyzed to NH4 +, whose uptake by plants may result in a dramatic pH decrease in the nutrient solution (Luo et al. 1993). Secondly, the presence of NH4-N instead of N03 -N in the nutrient solution may interfere with the uptake of nutrients, particularly cations (Barber 1984). Another problem is that plants grown with urea without Ni supplementation accumulate urea and show chlorosis or develop necrosis of the leaf edges (Gerendas and Settelmacher 1997b).


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## Edward (Apr 11, 2005)

More about urea http://www.plantedtank.net/forums/1...monium-sulfate-experiment-4.html#post10766282


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## Anon (Mar 16, 2014)

Hi Folks,

Well, it looks like I'm a few years late to the party! But, not to worry as this is one of the most interesting threads I've read for some time. And I have learned a lot from reading each and every one of your posts - several times over. I have just started experimenting with urea in a planted tank with no livestock. The tank has Java and Congo Ferns plus floating Amazon Frogbit. I added the first dose of urea yesterday to the tune of 0.6 mg/l. This has been repeated today. As there is no livestock in the tank right now, I'm not too concerned if pH is slightly above 7.0. But, I do have a Seachem _Ammonia Alert_ in there to let me know if free ammonia is considered safe to livestock (<0.02 ppm).

I spent a good deal of time deciding which urea product to use. That's because I quickly became aware that some agricultural urea, for example, can contain biuret and significant amounts of heavy metals. My hunch was that this could pose a problem to any livestock. I finally chose a pharmaceutical grade urea*, which may be over-the-top but I thought it was a risk worth minimizing.

I will further add to this thread as time elapses if anyone is interested.

*whose name I don't wish to disclose at present

Anon


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