[JamesC]

One question that has never been explained to me is why do some manufacturer's use ammonium or urea based compounds in their products as a source of Nitrogen. On all forums I visit it is drummed into you how adding ammonium and urea to your planted tank will create algae mayhem and that potassium nitrate is the way to go. Do the manufacturers know something? I even tried replacing potassium nitrate with urea keeping the N amount the same for several weeks but didn't notice any difference in plant growth nor did I suffer any algae outbreaks.

James

 

[jmhart]

I've been involved in a few discussions about this, and the result was that most people that have used urea have had absolutely no negative results. Positive results are pretty subjective, but I believe *technically* nirtrogen from urea is more readily available to plants, so again, *technically*, urea is a better option.

Why we all use KNO3, I don't know except that we all operate off that conventional wisdom that urea or NH4 will cause an algae bloom.

This is, of course, in plant only tanks.

 

[BryceM]

It's a pretty controversial topic. There are plenty of people who add nitrogen in the form of either ammonium or ammonia. Actually, they're one and the same, since one is quickly converted to the the other at a ratio that depends on the pH of the water it's placed into.

As long as you keep concentrations quite low, you'll probably do just fine. Plants actually have an easier time assimilating ammonium than nitrate from a biochemical point of view. They do just fine converting nitrate to a usable form though and it's infinitely less toxic to the fish.

 

[Zapins]

Nitrogen also lingers in the aquarium a little longer than the other forms. Some plants have a little bit of a hard time absorbing nitrates vs. urea or ammonia.

It makes more sense to dose all three forms in very low levels. If you look at nearly all garden fertilizers they always have a combination of all three compounds for best results. Just make sure that the total N level doesn't exceed the needed N level if you decide to dose.

I believe freemann has been dosing ammonia for a long time now without problems.

 

[AshK]

According to what I've read by Dianne Walstad, the vast majority--if not all--truly aquatic plants uptake ammonium more readily as a nitrogen source than nitrates. Only marginal plants found around a water's edge use nitrates more readily.

http://www.aquabotanic.com/plants_and_biological_filtration.htm

From what I've learned in botany classes, beneficial bacteria on plants convert nitrates quickly enough into ammonium for plant uptake. Because of this, I choose the "safer" route of using nitrates as a nitrogen source. I don't know if in actuality its "safer" or not, but after witnessing the damage of ammonia poisoning on fish I get a little uneasy around the A-words :shock:.

I look forward to reading more posts in this thread. Hopefully someone with first hand experience dosing ammonia/ammonium/urea will chime in and enlighten us.

 

[wet]

I've done this with Calcium Ammonium Nitrate (C.A.N.) but only induced greenwater, and I believe it to be my fault. At that point and with my amateur plant nerd understanding of chemistry I could not isolate NH4 uptake to plants, bacteria, or the greenwater, but N was gone all sorts of fast.

For those not aware but considering doing this experiment, remember to isolate N, by the way. For example, if I dropped about 10g of NO3 into my imaginary but awesome ginormous tank, I'd only need about 3g NH4 for the same dose of Nitrogen.

 

[JamesC]

I have decided to give dosing urea a go and see if there are any benefits. All plants currently grow great except for two. These are Alternanthera Reineckii 'lilacina' and Ludwigia Glandulosa which seem to grow with small and deformed leaves. I could of course always ditch these two plants but I like to persevere with them. I have tried different dosing stratergies from heavy EI through to a fairly lean dosing system that I currently use. Actually I found the heavier I dosed the worse the problem became with these two plants.

Been dosing urea for a few days and so far no problems. I'm adding 0.5ppm urea daily and have reduced the potassium nitrate so that the total nitrogen has remained the same. Potassium sulphate has been increased to compensate for the reduced potassium from the KNO3.

What I'm looking for is obviously an improvement in plant growth but also how nitrate levels change. If they drop then this would suggest that the plants are using the urea, but if they remain the same then this would suggest that the filter is getting to the urea first and converting it to nitrate. Because urea has a very high N content I'm now dosing about a third of the potassium nitrate as I was before, which is quite a difference.

I'll update this thread on any progress.
James

 

[Mr_docfish]

I have been dosing NH4NO3 for some time now... 1.5g per 1000l daily. I do have a 9W UV unit running 24/7 as I have 450Watts of MH lighting the tank with CO2, so I am asking for green water if I add NH4.
down side is the leftover H+ that will slowly drop the pH.... I do a trade off with adding Ca(OH)2 every week. I test the water weekly, particularly the pH after allowing it to stand for 24hours to let off the dissolved CO2. I also add KHPO4 for the PO4 levels, so the amount of Ca(OH)2 will vary according to the amount of NH4NO3 and KHPO4 added to the tank on top of the normal organic acids being produced.

 

[JamesC]

It's been two weeks now since I started dosing urea and I have noticed a dramatic change in my Alternathera Reinekii and Ludwigia Glandulosa. Both are now producing much larger and non-crinkled leaves compared to before, which I must admit has surprised me. All other plants are growing exactly the same as before except maybe the Rotala Macrandra which seems to look fuller and healthier.

This better growth could be due to the added urea but it could also could be due to the lower levels of nitrate that I've been dosing. Next step is to increase nitrate levels again and see how the plants react.

There have been no noticeable effects to fish or shrimp and also no algae problems.

James

 

[Coralite]

Aquatic plants have a negatively charged surface. Ammonium is positively charged so it takes less energy for plants to uptake NH4 than NO3 which is negatively charged. If I was just growing plants I would add ammonia as needed but seeing as I like to keep the nitrogen availability high, if I dosed ammonia at the same concentration as NO3 my fish would die.

JamesC, I would like to hear/see more about the change in the leaf appearance you've noticed by dosing ammonia.

 

[BryceM]

Aquatic plants have a negatively charged surface. Ammonium is positively charged so it takes less energy for plants to uptake NH4 than NO3 which is negatively charged.

Yes, polarity of the ions is one of the important factors, but the biochemical pathways are far more complex than this simple explanation. Cell membrane physiology as it relates to nutrient uptake is quite interesting. This process is highly regulated by the needs of the cell and different species utilize different strategies for assimilating nitrogen.

The enzyme mediated biochemical reactions that take place inside the cell allow most plants more than one option to assimilate nitrogen from the environment. Depending on the species, NH4+ is more easily assimilated (requiring less energy expenditure) than nitrate, nitrite, urea, or atmospheric N2.

The whole process is quite interesting and worthy of a far deeper discussion than usually takes place on a hobbyist level. If I get a minute, I'll dig into my old texts to see if I can find something that will shed some light on the subject.

For starters, this goes over just a few of the most basic aspects of nitrogen fixation from the form of N2 to NH4. This doesn't really answer the question of the the preferential source of nitrogen for aquatic plants, but it does shed a bit of light on the complexity of the invovled biochemistry.

The subsequent chapters address some of the nitrate/ammonium pathways.

 

[Coralite]

Hey Bryce,
Thanks for the elaboration. I know I was oversimplifying and I would love to hear an abridged overview of how different ions travel from the water through biochemical pathways to where they are used by plant physiology.

 

[JamesC]

JamesC, I would like to hear/see more about the change in the leaf appearance you've noticed by dosing ammonia.

Before dosing urea

After dosing urea

James

 

[kekon]

I also used urea. Moreover, i dosed 3 forms at the same time (NO3, CO(NH2)2 and NH4). I also noticed bigger leaves grow on some plants. The point is (but i'm not 100% sure yet) that by dosing urea and NH4 one can keep lower NO3 levels but maintaining the same growth which is achieved by dosing only NO3 but in higher levels. I didn't notice issues with any type of algae. I was encouraged by "Drak" firm which produces N fertilizer for planted tank which includes 3 forms of nitrogen. The daily dose is 1 ppm NO3, 0.1 ppm NH4 and 0.33 ppm urea.

 

[Amoeba1]

Hi James, what are your observations after dosing urea together with NO3?

 

[Zapins]

Hmm... any updates on using ammonia or urea in lieu of NO3?

 

[JamesC]

Funny you should mention it as I've just stopped dosing the urea about 3 weeks ago and gone back to straight potassium nitrate. So far to be honest I haven't noticed any real change so am now coming round to the idea that perhaps it wasn't the dosing of urea that had the effect as during the dosing of the urea I also suffered stunting at times.

I still have the Ludwigia Glandulosa which sometimes grows fine and other times doesn't. I'm still at a loss as why it happens. And before others jump in and say CO2 I'm going to say that I've had CO2 and flow levels really high and have also given the Ludwigia Glandulosa it's own personal supply of CO2 mist. I'm now strating to believe that it is to do with growth rates and that trying to make it grow too fast causes the deformations. I've dropped the T5's in favour of the old T8's and will note to see if this makes any difference.

One thing I have noticed is that the blyxa japonica does a lot better with higher nitrate levels.

James

 

[Mr_docfish]

One thing I have noticed (it was obvious after I finally thought of it) is I have been using ammonium nitrate NH4NO3, and testing weekly for nitrate only.... I have been keeping the NO3 at 15-20ppm, and now I keep it at 10ppm.... with much better results now.... I was over dosing the total N by not considering the NH4.....
I feel silly having said this, I should have noticed a long time ago.

 

[kekon]

I still have the Ludwigia Glandulosa which sometimes grows fine and other times doesn't.

I saw similar effects and it seems better growth occurs when NO3 is lower.
Blyxa Japonica is a plantwhich really appreciates high NO3 levels; i've never had any issues with this plant. I grows like a weed at NO3 10 ppm or more but some plants are severely stunted.
I'm still waiting for my ordered circulation pump but i think it will not help much.
I noticed that NH4 and urea work better in very soft water. In harder water NO3 is better. Generally speaking it seems that the harder the water the more NO3 can be dosed without harming the plants.

 

[nfrank]

i have been re-doing my dry fert regime... both in composition and amounts..... and have been thinking about adding additional N (without adding more K) to supplement what i provide thru weekly water changes. In the past i have used NaNO3 to supplement KH2PO4 and KNO3. This is not ideal since sodium nitrate adds unnecessary Na+, I am now considering urea and figured i would join this discussion.

Conceptually, urea is more appealing to me than NH4NO3 (as used by some products, like Amano's)... and maybe safer if overused, since it takes a few days for residual material to convert to NH4. Because i have choromines (NH2Cl) in my tap water, i am already providing some type of NH4 salt in potentially large amounts after a water change. The average chloramine concentration of Raleigh tap water is 3.5 mg/L!! I now live near the water treatment plant, so i expect my level to be on the high side. Adding prime breaks the NH4 chlorine bond and yields some type of ("detoxified")ammonium salt. So, a 50% water change can be provding a large amount of this stuff. No wonder the plants pearl like crazy (OK, some of that is due to dissolved gases )

I came across this article which talks about fate of urea in the aquatic environment. http://www.cryotech.com/products/pdf/ureafate.pdf It says that "urea completely degrades within 4 - 6 at 20degC" (into CO2 and ammonium). Based on the 40ppm "allowable" levels for salminid species, there is a reason to be somewhat comfortable with dosing of 0.5mg/L as used by the previous posters to this thred. I previously recommended short term concentrations of NH4 not to exceed 0.1mg/L.
http://www.thekrib.com/Chemistry/ammonia-toxicity.html

Seems like urea (in dry form) can be used at higher levels than NH4. It also provides a little bit of CO2