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How to balance NPK, Ca, Mg and micros - new experiments

73456 Views 73 Replies 21 Participants Last post by  trilinearmipmap
I was invisible on the forum as i was experimenting very hard and i have some new experiences i want to share with you. I gathered all the things i did during last 20 months.
The post also explains how to eliminate the most common problem such as stunted tips, curled and deformed leaves. Also, i think it's the highest time to disprove some theories such as "K blocking Ca" (it does, but to some extent only), "add more KNO3", "more CO2" etc. :) As usual, i use pure RO water in order to know all the elements concentration in the tank water (obviously RO filter doesn't remove all the impurities from the tap water but we can assume that those are at vero low, negligible levels). Recently i have switched to my own micro fert and i obtain better results that using commercial ones. Besides it's much, much cheaper solution. It's a pity i can't post some photos here i took during experimentig because i've reached upload limit... I hope the text i've posted will describe my experiments well.

The story about Ca, Mg, N, P, K

Compounds used to fertilize the tank:

1. CaCO3, CaSO4*2H2O (as a source of Ca)
2. Anhydrous MgSO4 (as a source of Mg)
3. CaCl2 (as a source of Cl)
4. KH2PO4 (as a source of P)
5. KNO3, CO(NH2)2 (urea) and NH4NO3, Ca(NO3)2*4H2O (as a source of N)

NO3 test kit (Hagen) was calibrated.
Water used during WC at the beginning of the experiment (all values in ppms):

Tank 200 liters, ligthting 160 W, temp. 24C.
Ca = 25, Mg = 5, Cl = 10, SO4 = 70..80, K = 10, NO3 about 10 ppm, PO4 = 1. KNO3 and CaNO3

Blyxa Japonica grows very fast; it constantly produces little flowers. Micranthemum Umbrosum is stunted. It grows extremely slowly; leaves are extremely small, griowing tips disappear. Alternatera Reineckii is severely stunted; new leaves are horribly twisted and deformed, growth is very slow. Rotala Indica grows very slowly as well, some tips are dwarfed. Glossostigma and HC grow pretty well. Cabomba caroliniana grows exceptionally fast and needs to be pruned twice a week. No algae.

change: NO3 was lowered to 5 ppm.
effect: Umbrosum and Alternatera began to grow normally, without deformations and stunted tips.

This lasted for about week and a half but the plants became stunted again. Potassium excess was suspected.

change: K was lowered to 5 ppm (5 ppm K added to changed water during WC; no K was dosed on
daily basis throughout the week)
effect: No change in growth. Old leaves on Bacopa Caroliniana rot and fell off. So it wasn't K

change: K was raised to 15 ppm in the water column.
effect: In 3 days Umbrosum and Alternetera began to grow healthy and fast, no stunted tips and
deformations on young leaves. All other plants started faster growth rate. Limnophila
Aromatica was producing new side shots. So it was K deficiency !
Now i decided to add 20 ppm K at every water change (to changed water) to keep this
level in the water column.

Classic definition of potassium defiency says, that it shows up as yellowing old leaves, pinholes and rotting. As i noticed in the experiment above, it can also appear on growing tips causing them to stop growing. Some sources confirm the fact (
It may resemble Ca deficiency in aquatic environment and we often confuse it with one.

Since i added 20 ppm K at every water change plants grew much better but some tips on Umbrosum and Alternatera were still stunted. I suspected that there was still not enough K (although it was 20 ppm K in the water column). It seems unbelievable.

change: an extra 10 ppm K dose was added to the tank. Now it was approx. 30 ppm K in the water
effect: in 3 days new side shots grew on the affected plants but most new leaves became pale.

It made me think that plants really needed high amounts of K. However, new shots stopped to growth shortly after extra 10 ppm K dose... Besides, most plants became unusually pale despite decent iron and manganese fertilization (0.35 ppm Fe and 0.2 ppm Mn weekly).
I was scratching my head of what is causing the stunting and pale leaves. There was one more deficienct element... Because there was plenty of K i had the right to suspect Ca deficiecy:

change: Ca was raised to 45 ppm (Mg was unchanged and maintained at 5 ppm in the water column)
effect: slight improvement was noticed but it was unacceptable, most new leaves became much

There was one element that i was afraid to add more - magnesium.

change: Mg was raised to 10 ppm.
effect: In 3 days all the plants started healthy ane faster growth. No stunted tips and deformations.
Several days after adding more Mg, pale leaves regained their natural colors. Some leaves of
Cardamine Lyrata curled upward along edges so it was a sign that there was slight Mg excess
for this plant.

change: because of slight Mg excess i reduced it to 8 ppm. Also Ca was reduced to 32 ppm. K was
dosed at a rate 20 ppm per water change (20 ppm to changed water, not to a whole tank !)
and additionally 1..2 ppm K daily.

effect: all the plants grow very well, they have rich colors, no algae, no stunting, twisting etc. Only
Rotala Wallichi grows very slowly and some tips are stunted. This plant is problematic for me
and i still don't know how to make it grow well. Changing different ratios and levels of
nutrients (including micros) doesn't have any effect on the plant.

So, now water paramneters at which plants are growing very well are as follows:

Ca = 32, Mg = 8, Na = max. 5, NO3 = 5, PO4 = 0.2..0.5, K approx. 30 ppm, Cl = 5,

I'm going to take water sample and bring it to the laboratory to get to know exact values of Ca, Mg and K.

"Rude" summary

It seems that stunting, twisting and deformations on new leaves are caused by:

- nitrogen excess at low GH
- too little Mg, K, and sometimes Ca
- too high Ca:Mg ratio (above 5:1; some plants don't care about it but it does matter for some

I forgot to add some more about NO3. Lowering NO3 always helped to eliminate problems with stunted tips but at lower NO3 (5 ppm) some fast growing species may suffer from N deficiency. To solve the problem while keeping low NO3 i introduced urea and NH4 into N fertilizer together with NO3. I simply made N fertilizer produced by German "Drak" company. The fertilizer is named "Eudrakon N" and daily dose adds to the tank:

1 ppm NO3
0.33 ppm urea
0.1 ppm NH4

Some of you may thing it causes algae bloom but it doesn't ! This fert works very well, plants love to be fed with 3 forms of N :) Using 3 forms of N we can keep low NO3 in the tank and have fast growth.

The story about micros

At the beginning of experimenting i used TMG fert on daily basis adding 200% of the recommended dose. However, it turned out to be too little. Because i use pure RO water, TMG fert has to be dosed much more than the recommended dose. I achieved good results at 250% dose + extra Fe and Mn. Of course it is too expensive, especially for larger tanks. When i added 200% dose Limnophila Aromatica grew slower and it produced tiny leaves placed very close to each other. I suspected zinc deficiency:

change: 0.02 ppm of Zn was added from zinc sulphate (ZnSO4*7H2O)
effect: in 4 days the plants bagan to produce normal sized leaves.

It turned out that zinc sulphate and chelated zinc EDTA type work well. I didin't notice difference between not chelated and chelated zinc, however it is safer to use chelated one. So i made my own micro fert and the weekly doses of micronutrients were as follows (all values in ppms):

Fe: 0.35
Mn: 0.2
B: 0.02
Zn: 0.02
Mo: 0.004
Cu: 0.008
Ti: 0.002
Ni: 0.001
Co: 0.001

compounds used:

- DTPA 7% Fe chelator ("Dissolvine D-Fe-7" made by Akzo-Nobel)
- Mn 14% Mn chelator (EDTA + some DTPA)
- Cu, Zn chelators (EDTA + some DTPA)
- ammonium molybdate as a source of Mo
- titanium solution 0.85% Ti (titanium acts as biostimulator but it is not neccessary for plants)
- nickel chloride
- cobalt chloride

Plnats grew quite well, but after some time some time (about 2 weeks) some new leaves on Rotala Indica bent downward and some leaves vere chlorotic. Boron excess was suspected.

change: i did 50% water change and weekly boron dose was limited to 0.008 ppm
effect: a few days after WC affected chlorotic leaves took normal colors, no more bent leaves grew.

Disiplis Diandra was one of plants that have too pale leaves, despite good Fe and other nutrients fertilization. Copper deficiency was suspected.

changed: daily Cu dose was raised to 0.012 ppm
effect: a week later, Didiplis had richer colors.

However i'm not quite sure if it was higher copper dose that helped. It can be caused by other factors but as i remember adding more Cu always helped Didiplis to take richer red colours on its tips.

Now i no longer use any commercial micro fert :) The only issue is how to preserve the solution from mould and preciptitating nutrients. To to this i add ascorbic acid (0.5 g / 1L). It preserves the fertilizer from oxidation. To prevent the solution from mould it is neccessary to use methyl paraben but i haven't managed to get one so far so i keep my fert in the fridge.

Sorry for such a long text but i hope it will help some of you to enjoy our hobby.
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Excellent and very intense examination of plant uptake and deficiency. I take it that plant growth was sustainable for 6 weeks or more once you reached your final choice of levels? Could you list the plant specie used in the experiment? J. Blyxa, D. Diandra, L. Aromatica, M. Umbrosium, B. Caroliniana, A. Reinecki, M. Umbrosum, R. Wallachi, R. Indica, and C. Lyrata I gathered from the above text. Any others? I think this could make a nice reference source once it's discussed.
Plants that were used:

- Micranthemum Umbrosum
- Alternatera Reineckii
- Blyxa japonica
- Rotala Indica
- Glossostigma Elatinoides
- Cardamine Lyrata
- Bacopa Caroliniana

- valissineria spiralis
- Anubias Barteri var. nana
- microsorium (i don't remember its exact name)
- elechoaris
- Rotala Wallichii

Plants species written in green color didn't react to any change in fertilization so i omited them in the desctription. All other plants responded exceptionally quickly to every change; however i tried to maintain any introduced change for at least 2 weeks. When i wanted to change any micronutrient i added desired amount of it directly into the tank and the effect was noticeable no longer than a week after addition. Changing K, Mg, N always gave results that were seen no longer than 3 days after the change. At decent lighting (0.75 W / 1L) plants respond quite quickly to changes.
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Kekon this is very good information. I think it's pretty silly of us to state that nitrogen needs to be kept between x and y, etc. As far as I'm concerned there is a growing body of evidence that nitrogen needs are much lower in systems with soft water.

As far as potassium is concerned, this is something that I've suspected too. Amano for one is very keen on potassium dosing but less enthusiastic about N and P except in cases of high-light, high-CO2, rapid-growth plant situations. I'm becoming gradually convinced that the typical EI methods of supplying K as a byproduct of dosing KNO3 and KH2PO4 probably results in too much NO3 and too little K in most situations, especially with softer water. I haven't had too many issues with tip stunting with my current fert regime except for with Pogostemon stellatus. I'm gradually cutting back on my NO3 and PO4 dosing which has helped with bothersome green algae on the glass. I've been thinking I'll need to start K2SO4 dosing at some point to avoid too little K. This will be a fun experiment.

Your writeup reminds me that I should look at this more carefully. Thanks for all of the info.

Regarding R. wallachi, some have found that Mg excess (over 10ppm) results in tip stunting, but this is nothing more than an anecdotal observation. Clearly the "rules" of dosing are highly dependent on the setup, lighting, CO2, substrate, and other parameters that are defined for any given question. It would be silly to assume similar results between a tank with an inert substrate, medium light, and hard water and a tank with ADA's Amazonia, high light, and very soft water.

My current "pet" theory is that very, very low N and P levels (by our current standars) are ideal, provided that they can be kept consistently present in stable quantities (just like nature - go figure!). Allowing a severe N shortage to develop (especially suddenly) is a great receipe for disaster. Nitrogen excess has always resulted in green crud on the glass in my tanks. Let's all remember that the addition of N and P to an aquarium was thought to be a disasterous idea even as recently as 10 years ago.
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I think the key to success is just not too much NO3, PO4 and harder water. The harder the water the higher NO3 can be kept without stunting. EI method works well but at harder water. I don't agree EI can be used in soft water. Some plants will do very well (Cabomba, Blyxa, Zosteriflia) but some will be severely stunted. To summarize all the things we should do the following:

- do not overdose NO3 (or NH4 if someone prefers this form of nitrogen). Depending on water
hardness it seems it should be kept no higher than 5 ppm when GH is in 3..7 range or higher than 5
ppm when GH is at least 8.
- add enough K to changed water and additionally every day (in my case 20 ppm in changed water
and 1..2 ppm daily works well). I've always thought K was the main culprit of stunting but now i'm
sure it is not - on the contrary - it helps to eliminate stunting.
- ensure there is enough Mg (Mg deficiency also causes stunting). It can be kept at 4:1 ratio and
this works well for most plants (32 ppm Ca and 8 ppm Mg works very well in my tank)
- do not add extra Mg if we use tap water and when we don't know how much Mg is there in the tap.
Overdosing Mg will cause new leaves to curl uwpard along edges or dwarfing some plants.
- do not add too much PO4. I noticed it doesnt't speed up plants growth. I keep 0.2..0.5 ppm
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Hi kekon,

very interesting experiment. I've changed my dosing routine to nearly your specs and it resulted in alot healthier grow in my semisoft water (gh 6-7). For the last 6 months i was unable to get very good growth with the estimative index and tried nearly everything to get more of the "missing" nutrients into the tank. I've rised iron and trace elements to really high levels (iron around 1-2ppm). Dosed magnesium, calcium etc. My CO2 levels have been really high during the whole time at around 40ppm with direct misting towards the plants (checked via drop checker and digital pH meter).
At all my growth was never satisfying :(. Now i've reduced my macro dosing alot and have switsched to Eudrakon N from DRAK for nitrogen supplementation, also i've upped my K dosis to 20ppm. My plants are getting better with each day.

The big question that confuses me is why some people are getting great results with EI even in soft water (Tom for example is using a GH around 5 or WolfenXXX has nearly no GH with pure Osmosis and no extra Mg and Ca addition) and i (and alot other) struggle with proper conditions.
The main argument for no success with EI is not enough CO2, but at my case it can't be that simple. High CO2 all the time and the plants are pearling like mad but at the same time not growing very good (stunting, curling and other deformations) :(. I even rised my GH to higher levels (GH 13) due to your last thread hoping that with those higher ca/mg values i might be able to keep NO3 around 20ppm levels. For example freeman with a GH at 12 is able to keep 20ppm of NO3 and alot other people too.

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EI method is good for many plants but not for all of them. I had some plants that grew like crazy under EI fertilization in GH of about 4..5: Blyxa, Cabomba, Zosterifolia. Other plants were horribly stunted and deformed. High CO2 levels didn't help. There was 50 ppm CO2 in my tank with no good effect. We don't have to believe entirely what T.Barr and Wolfen say. They don't know all the water parameters they have in their tanks. They didn't have all the plants species either. It's very easy to patronize someone how to do things when they work very well for them. But in my opinion, one must analyze someone's problem first before telling how to solve it.

I notice that high N and P levels are not good for plants. They do better in lower NO3 and PO4 levels. However, K must be kept at high levels.
I imagine such a situation (i don't mean to offend him; i know he's extremely good at the hobby): T.Barr comes to my house and sees stunted plants in my tank:) Then he tells me:

"bring me those bags of KNO3 and KH2PO4"

Then he takes a few big spoons of KNO3 and KH2PO4 and pours them into the tank... Also, he increases CO2 valve to set 3..4 bubbles per second. He takes a bottle of TMG and pours some into the tank. And what will we get 3 days later ? Deformed, twisted and curled leaves on many plants... I did the same routine in the past with the same effect.

Now i keep GH of about 6..7, NO3 5, PO4 0.2..0.5, K 20 ppm added to changed water and 2 ppm daily. Under those conditons plants grow much, much better; they have rich colors. I no longer have issues with stunting. It seems that K is very important factor to succesfully grow aquatic plants. Also, Mg must be taken into account. Mg and K deficiency may look nearly the same - lack of these elements can cause disappearing of growing tips and deforming of young leaves (most folks may disagree as they believe that Mg and K deficiency appears as yellowing on younger leaves only)

p.s. I also use Eudrakon N :) It's very good N fertilizer. However, i make it myself because i have lots of KNO3, urea and NH4NO3 which the fertlizer is made of.
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Interesting thread indeed!

I also had some stunting problems and curly leafs (especially Alternanthera) now and then on some species for a long period (1-2 year).
I'm using the EI method with 50% wc per week and do not measure any nutrients at all. However, I put a lot of focus on measure and sampling data of the CO2 in the tank to make sure I have enough every single hour every single day. I have been dosing in the range of: 10-15 ppm N, 1-4 ppm P, 10-15 ppm K, and 0.1-0.2 ppm Fe (Micro+). I have soft water from the tap (20 Ca, 4 Mg) and I've tried to boost up to quite high levels without success.

Five weeks ago a bought some test kit's ( ) and started a new approach with much lower nutrient levels and the tank is now running very well without stunting plants and curly leaves.

My new dosing regime:

After wc I add:
6 ppm N + 4 ppm K from KNO3
5 ppm K from K2SO4
0.25 ppm P from KH2PO4
No extra Ca/Mg is added at all.

Now my remaining issue which confuses me a lot - trace elements.
I have to add 0.2 ppm (no more no less) from Micro+ every single day. I also have to add it in the morning otherwise the level is zero after one night. Ok, I know test kits are sometimes confusing and messing things up but I trust the JBL quite well. It shows me exactly what I'm dosing!!

I'm just wondering where all the traces (Fe) are absorbed? By the plants, filter, substrate - who knows? I have checked the filters and there is no miscolour from Fe. I can hardly believe that the plants uptake is so big. Substrate - hmm...maybe.
By in fact, the tank is now running week after week very well without algae:
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Most of Fe and Mn (so do other micros) precipitate. Canister filter also absorbs large amounts of Fe.
I think that oxygen which is dissolved in the water in quite large amounts is the main cause of destroying Fe compounds even when Fe is chelated by strong chelators.
The mulm which is produced in the filter (looks like mud) contains lots of oxidised Fe. I was advised to clean the filter more often because mechanical media - when they get dirty - they absorb more and more trace elements. When i bagan to clean my filter more often it had good effect for plants - they got richer colors. It seems that manganese is prone to oxidation and precipitation much more than iron. Some people i know measured Mn in a laboratory and the results showed values close to zero despite high amounts of Mn added into the tank.
I think that oxygen which is dissolved in the water in quite large amounts is the main cause of destroying Fe compounds even when Fe is chelated by strong chelators.
Interesting. I've seen once that the Fe uptake was decreased when the CO2 was unintentional lowered for a day and perhaps the oxygen level as well (less plant perling/bubbels that day)?

The mulm which is produced in the filter (looks like mud) contains lots of oxidised Fe.
I thought the filter media turns more red if there was lot of Fe?!? My are "normally" black/brown:
My filter media look exactly the same before cleaning :)

I thought the filter media turns more red if there was lot of Fe?!?
I've never noticed that but as far as i know many iron compounds turn into rust which takes brown colors. However in a planted tank the filter also gathers many other organic particles which in contact with iron cause filter media take black colors (i think it's mostly caused by bacteria activity)
Thank you for share.
Did you measure TDS in the experiment?
If you did it, could you list TDS values of the experiment?
Unfortunatley i've never measured TDS... but i can list all the values and chemical compounds i add to my tank during RO reconstitution as well as during daily fertilization:

RO Reconstitution:

Ca - 29 ppm (CaCO3) + 2 ppm (CaCl2) = 32 ppm
Mg - 9 ppm (anhydrous MgSO4)
K - 20 ppm (K2SO4)
Cl - 5.1 ppm (CaCl2)
Na - 0 ppm (but small Na amounts comes from DTPA chelator, but i don't know how much)
SO4 - about 60 ppm

Daily fertilization:


NO3 - 0.5..1 ppm (KNO3 + NH4NO3)
NH4 - 0.05..0.1 ppm (NH4NO3)
CO(NH2)2 (urea) - 0.33 ppm
K - 1..2 ppm (KHCO3)
PO4 - 0.2..0.25 ppm (KH2PO4)

micro (also daily doses):

Fe - 0.05 ppm (DTPA "Dissolvine D-Fe-7" produced by "Akzo-Nobel")
Mn - 0.029 ppm (EDTA + DTPA Mn chelator; 14% Mn)
Zn - 0.00285 ppm (EDTA + DTPA Zn chelator; 14% Zn)
Cu - 0.0017 ppm (EDTA + DTPA Cu chelator; 12% Cu)
B - 0.0014 ppm (H3BO3 - boric acid)
Ni - 0.000143 ppm (NiCl2*6H2O)
Co - 0.000143 ppm (CoCl2*6H2O)
Ti - 0.00043 ppm ("Tytanit" liquid biostimulator)
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Bluesboy, this is a bit off Kekon's topic, but I'd guess that your iron is forming insoluble complexes and falling to the substrate. It probably doesn't stay in the water column very long.
The one thing that puzzles me about that is the Cl. I know cloride from things like NaCl and CaCl have quite a negative effect on some plants growth even in small amounts. When I was useing CaCl to dose calcium I had mixed results in that being any help for the cupped leaves caused by Ca shortages.

And Cl2 we try to remove from the water if we are keeping any organisms.

I'm at a loss to explain why either would be dosed.
Cl (chloride, an ion) is a required nutrient for both plant and animal growth. Don't confuse this with Cl2, which is chlorine the gas. They may be a bit similar from an elemental point of view but their chemical reactivity and biologic action are completely opposite.
I hope this is on topic because it's how to balance makro and micro.

Bluesboy, this is a bit off Kekon's topic, but I'd guess that your iron is forming insoluble complexes and falling to the substrate. It probably doesn't stay in the water column very long.
I have done some tests. At the same time I took a water sample from the substrate (under the gravel and just above the bottom glas), and one from the water column.
I have measuerd NO3, PO4, pH, kH and Fe. All are the same except the Fe. It's out of range in the substrate (on the right-hand side):

I wonder why the Fe is absorbed in the substrate and why it's still measureble by the Fe-test
:confused: Any ideas?
I have some doubts concerning Cl. I used CaCl2 but in small amounts; the Cl concentration has never been higher than 15 ppm. I didn't notice any issues at such Cl level but perhaps it was too short period (2 weeks) to confirm it was safe for plants.
Some folks reported problems using CaCl2 but i think they used much of it. I've never known how much Cl plants really need. Rivers and lakes that are not contaminated and where aqautic plants grow, usually have low levels of chlorides - no more than 5 ppm (i read about it from literature available in the internet). In tap water however, we often measure much higher levels of chlorides. It's usually 10..50 ppm ppm or higher. Maybe some issues he have with our plants are caused by higher Cl levels but i'm not sure. The strange thing is that higher Cl levels in the tap are not as harmful to plants as the same Cl levels added artificially from salts such CaCl2 or NaCl for example. Anyway, i try to add no more 10 ppm Cl when i reconstitute RO water. I know that KCl (potassium chloride) is safer than CaCl2 (as a source of Cl only).
When it comes to SO4 i didn't see any negative effects even at higher concentrations close to 100 ppm.
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There is a thread here that discusses some experience with using CaCl to dose calcium to high levels for inverts. These guys also keep plants and experienced a great change in growth in a positive direction when they switched to a different source of Ca.

My understanding from reading the above thread and documents linked to in that is that Cl levels can inhibit plants ability to uptake N, and that different plants have different tolerance levels for Cl.

If you know you aren't getting Cl from any of your other dosing compounds I might treat it like a micro nutrient and take it back to a .5-1 ppm level.
Kekon, where do you keep your level of iron?
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