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 (http://4e.plantphys.net/article.php?ch=t&id=289
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):
- 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.