Aquatic plants prefers ammonium over nitrate

[Navanod]

Hi All,

Was researching into the potentials of using ammonium nitrate as an N source (as opposed to calcium nitrate, with obvious benefits of not having to worry about high Ca) and came across this article

http://www.aquabotanic.com/plants_an...filtration.htm

The results and findings are encouraging for those of us who have fast growing plants in our tanks. However, this article also overturns some common beliefs and in certain cases, made me think really hard if we're dosing our tanks correctly. I have some thought and questions that the gurus and experts may have better insights to:

1. We normally term certain plants (eg hornworts, frogbit etc) as "nitrate sinks". Should we look upon them as ammonia sinks instead? Most hobbyists see the nitrogen cycle as livestock-NH3-NO2-NO3-plants, with plants as the final sink for the nitrate. What if NO2 and NO3 are not really relevant for tanks with high grown plants?

2. If they're indeed ammonia sinks, that's all well and good for folks who do not want to go through the pains of cycling their tanks for weeks and months.
However, does this also means that these tanks will almost never truly cycle (ie. the required bacteria will never reach a critical mass that can handle the actual ammonia output of the bioload) since much of the ammonia is uptake by plants?
Would ammonia spike and mini cycles occur if heavy pruning of the plants take place?

3. Since we're dosing exclusively nitrates for EI, what happens in tanks with high bioloads? The plants would actually prefer the ammonia from the livestocks over nitrate so these added nitrates would simply remain untouched and wasted, although toxic buildups are unlikely given the 50% waterchange in EI.

4. What is worrying is that in the presence of ammonia, nitrate uptake in certain plants stall and only restarts upon depletion of ammonia. In a tank with small amount of ammonia constantly being produced by livestocks,what's actually happening? Would the plants slow down because they are waiting for ammonia although there're tonnes of nitrates around?

5. My initial intent was to find a way to easily degrade the ammonium nitrate into a pure nitrate solution. With 2N per molecule, this will be a perfect substitute (at least for the N portion) of KNO3. The explosive precusor act allows NH4NO3 of 60% of less to be sold, and thats more than enough for fertilizing requirements.
However, if the plants actually prefer ammonia, is there a safe way to direct-dose NH4NO3 as part of EI although conventional wisdom always calls for ammonia and nitrite to be 0 in a tank?
Since NH4+ is less toxic and formed under acidic conditions and low temperatures, (http://www.thekrib.com/Chemistry/ammonia-toxicity.html) tanks with such conditions may actually be able to tolerate ammonium nitrate dosing?

Any thoughts gentlemen?
Thanks

[Navanod]

http://www.dataguru.org/misc/aquarium/AmmoniaTox.html

Ouch, these tables would certainly come in useful if I ever need to know how much NH4+ to have in the tank...

[GaspingGurami]

Erm.. Ammonium Nitrate is usually sold as a prill. The Ammonium is on the outside covering a nitrate inside. It is used by terrestrial gardeners as a 2-in-1 fert. For Initial growing stages of a plant, it grows better with a cationic Nitrogen source eg Ammonium. After 60 days of growth, the ammonium "shell" of the prill will be exhausted releasing the nitrate core. At this stage the plant is made ready for blooming and reproduction when it changes its feeding to anionic Nitrogen eg Nitrate.

I don't think Ammonium Nitrate will work for aquariums. If the pH is high, the ammonium converts back to Ammonia, which will quickly degass out to the atmosphere, but not before wrecking havoc on the livestock. If pH is low, excessive ammonium is still bad for livestock as it will convert to Nitrite. If you want to experiment with ammonium without the hassle of the explosives act, you can easily get Ammonium Sulphate from Dr Mallick.

BTW, the plants are not exactly "ammonia sinks" nor "nitrate sinks". They are better thought of as Nitrogen sinks, in your aquarium as they convert the nitrogenous compounds (ammonia, ammonium, nitrite, nitrate, urea) into protein that build the plant's cells.

HTH

LL

[Navanod]

Thanks for your reply LL. Unfortunately, I'm also trying to avoid any sulphates (ie. potassium sulphates) as Shadow has experienced loss of livestocks dosing that. Also, there's less N in that and I'll have to deal with excess S...
Haha, I can see the paradox of being careful with sulphates but trying to play around with adding ammonia to the tank!!

The other option for N would be the calcium nitrate that most are using...anyone knows what is the toxic ppm levels for calcium? I'm already adding shrimp related products that would probably add calcium already

Actually...this prill sounds really interesting...if one can somehow dissolve or remove the outer ammonium coat away, then we'll have nitrate, but nitrate what? Don't think either ammonia or nitrate is offered as a stable compound on it own? I thought the prill is just a ball of compacted ammonium nitrate?

[GaspingGurami]

Potassium Nitrate is 13:0:44
Calcium Nitrate is 15:0:0
Ammonium Sulphate is 21:0:0
Ammonium Nitrate is 33-34:0:0
Urea is 45:0:0
Diammonium Phosphate (DAP) 18:46:0
Mono Ammonium Phosphate (MAP)11:48:0

These chemicals above all provide Nitrogen to your plants, although Ammonium and Urea are bad for livestock's health. I've not encountered excess calcium problems ever since I switched to Calcium Nitrate but YMMV. BTW the calcium from CaNO3 does not raise the water pH, and plants are happier with the Ca since our tap water is very low in hardness.

Loss of livestock may be more due to the K than the amount of S in the water. Potassium affects the cell pressure, and excess can kill. That's why Potassium Chloride is used for executions in some countries. In the past, when KNO3 was freely available, dosing K2SO4 can cause casualties due to the high K content (44%) already in KNO3.

HTH

LL

[Navanod]

I wish I can still get potassium nitrate
Back to the drawing board I suppose...maybe a mix of calcium nitrate and tiny bits of ammonium nitrate...the others on the list are more of a problem to use...

[GaspingGurami]

Erm.. Ammonium Nitrate is usually sold as a prill. The Ammonium is on the outside covering a nitrate inside. It is used by terrestrial gardeners as a 2-in-1 fert. For Initial growing stages of a plant, it grows better with a cationic Nitrogen source eg Ammonium. After 60 days of growth, the ammonium "shell" of the prill will be exhausted releasing the nitrate core. At this stage the plant is made ready for blooming and reproduction when it changes its feeding to anionic Nitrogen eg Nitrate.

Correction: The nitrate is on the outside of the prill and the ammonium encased inside. The plant takes up the anionic Nitrates first for vegetative growth, then after 2 months or so, converts to taking in the cationic Ammonium which stimulates reproductive growth.

Dunno how to edit my posts with this new layout.

[GaspingGurami]

I wish I can still get potassium nitrate
Back to the drawing board I suppose...maybe a mix of calcium nitrate and tiny bits of ammonium nitrate...the others on the list are more of a problem to use...

Calcium Nitrate has 15% N content compared to KNO3's 13%. (note that the tiny 2% difference is a lot, as 2% = 20,000 ppm).

So if you are dosing CaNO3 in the same amounts as you do with KNO3, you will be adding more N to your tank than you used to do. Why do you need to add more Nitrogen in the form of ammonium? If you are thinking of the K component of KNO3, you can always add KH2PO4 which will give your plants both K and PO4 in a nicely balanced package.

HTH,

LL

[Navanod]

Calcium Nitrate has 15% N content compared to KNO3's 13%. (note that the tiny 2% difference is a lot, as 2% = 20,000 ppm).

So if you are dosing CaNO3 in the same amounts as you do with KNO3, you will be adding more N to your tank than you used to do. Why do you need to add more Nitrogen in the form of ammonium? If you are thinking of the K component of KNO3, you can always add KH2PO4 which will give your plants both K and PO4 in a nicely balanced package.

HTH,

LL

Thanks for the clarifications above on the prill. I think you cannot edit posts after a certain time has lapsed.

Erm, the Calcium nitrate does not have more N%. Its only 11.86% vs KNO3's 13.85%. So We're actually 2% short.
But after checking up on the recommended Ca ppm in Shadow's calculator, I was pleasently surprised to find that its quite high and can be up to 30ppm! So you're very right that dosing Calcium nitrate is good for the plants and I probably should not worry about calcium overdose. Guess I can drop the idea of using ammonia unless its a purely planted tank without livestocks. Thanks for clearing my confusion

I am using KH2PO4 but its more for the P than the K. Unlike the calcium, the EI dose for P is only 2ppm. If I were to dose KH2PO4 to get the 30ppm of K, I'll be overdosing P at 35ppm when only 2ppm is required. If I dose to get only 2ppm of P, then it'll only be 0.9ppm of K.
I'm thinking of using Potassium sulphate but to get 30ppm of K, it'll also dump 12ppm of sulphur into the tank, not very tempting...maybe a cocktail of Potassium sulphate, chloride and bicarbonate? Hahahaha

[StanChung]

My thought is that plants would eat any of the three/four versions of N.
Ammonia is abundant in Aquasoil hence the preference of fishless cycling and also extra care in lighting to prevent green water.

I always thought sulphates are more toxic than K. Each time I dose K2SO4 the shrimps die.

[Navanod]

My thought is that plants would eat any of the three/four versions of N.
Ammonia is abundant in Aquasoil hence the preference of fishless cycling and also extra care in lighting to prevent green water.

I always thought sulphates are more toxic than K. Each time I dose K2SO4 the shrimps die.

Thanks for confirming the reports that excess sulphates are not good for shrimps...how much K2SO4 did you dose if I may ask?
Have you tried using KH2PO4 at high dosage for the K? Thanks

[StanChung]

I'm very sorry this is not very scientific but this was what I did.
50% K2SO4 50% KNO3. Dissolve till everything in 5 liter of water till saturation. 5liters water for about 1kg total salts.
Whatever undissolved, I just add more water to water plants. Normally just a bit at the bottom.
This ratio proved bad.

Reduced it further 30/70, slight improvement but not conclusive. Overdose a little and death.
My dosage is standard 1ml/20L

So I decided to try just K2SO4. Put in a pinch-1/4 teaspoon in my two feet tank[60L] weekly but this proved disastrous too.
KNO3- no problem.

So my amateurish conclusion is there is something toxic about -SO4.2+
I could be wrong. Sorry I'm not good at calculating ppms because I don't have an accurate scale that can measure gram fractions.

[Shadow]

since you want to make KNO3, why don't use Ca(NO3)2 and K2SO4? Both are available, at least not ban yet.

K2SO4 + Ca(NO3)2 -> 2KNO3 + CaSO4

You can seperate KNO3 and CaSO4 because CaSO4 is insoluble and will precipitate

I have not try it yet, so can't really tell much.

[Navanod]

I'm very sorry this is not very scientific but this was what I did.
50% K2SO4 50% KNO3. Dissolve till everything in 5 liter of water till saturation. 5liters water for about 1kg total salts.
Whatever undissolved, I just add more water to water plants. Normally just a bit at the bottom.
This ratio proved bad.

Reduced it further 30/70, slight improvement but not conclusive. Overdose a little and death.
My dosage is standard 1ml/20L

So I decided to try just K2SO4. Put in a pinch-1/4 teaspoon in my two feet tank[60L] weekly but this proved disastrous too.
KNO3- no problem.

So my amateurish conclusion is there is something toxic about -SO4.2+
I could be wrong. Sorry I'm not good at calculating ppms because I don't have an accurate scale that can measure gram fractions.

No kidding man! 500g of KSO4!! Thats about 18000ppm of sulphur in that 5L of water!

since you want to make KNO3, why don't use Ca(NO3)2 and K2SO4? Both are available, at least not ban yet.

K2SO4 + Ca(NO3)2 -> 2KNO3 + CaSO4

You can seperate KNO3 and CaSO4 because CaSO4 is insoluble and will precipitate

I have not try it yet, so can't really tell much.

Thats brilliant~!!! I've been looking at breaking down and degrading ammonia but completely missed this! CaSO4 is plaster of paris! I can use the by products for arts projects! hahaha~!
If this can work,

[StanChung]

Looks like I'll always be loyal to LFS for being lousy at chemistry..