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Maq's Substrate Experiment

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Day 29 (Jan 5): Water change 50 % with remineralization.
Day 31 (Jan 7): Fertilization: boron 1.6 µg/L, manganese 4.1 µg/L, zinc 1.6 µg/L, copper 0.48 µg/L. Measuring:
1704635514857.png
Some microbial spots appeared, first in tank D. It's too early to say it's algae, or fungi, or merely bacterial biofilms on side and rear glass.
In tank B, Ammannias show some signs of stunting, malformed leaves. Too early to show on photographs. We shall see later.
 
Hi @_Maq_ , your experiment seems very interesting to me (although I am a newbie). Once I read somewhere that substrates with high CEC (like your aqua soil) should be "hungry" meaning that they "eat" cations in exchange for hydrogen which should quite dramatically lower pH. But in your tank C the pH seems to be same. How do you explain it?
 
Hi all,
27482 said:
Once I read somewhere that substrates with high CEC (like your aqua soil) should be "hungry" meaning that they "eat" cations in exchange for hydrogen
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Yes, they exchange cations from the water column with the bound cations on their exchange surfaces. <"https://www.grainsa.co.za/soil-the-...t--part-9-cation-exchange-and-base-saturation">. If you start with protons (H+ ions) on <"the exchange surfaces"> they will be exchanged for ions in the water column, and particularly with those of higher valency (like Ca++ etc). <"Cation exchange isn't entirely straightforward">, and depends on the concentration of ions in solution as <"well as their atomic radius and valency">.
Dolos M said:
they "eat" cations in exchange for hydrogen which should quite dramatically lower pH.
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Unfortunately pH isn't entirely straight forward either, but "yes" acids are "proton donors" and you've added a proton via ion exchange.

cheers Darrel
 
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To Darrel: Yes, that's what I have read, but my question was pointing rather to "how do you explain that in tank C (where this increase of H+ ions should happen and thus pH should drop) this does not happen"? This seems strange to me and contradictory to your description as well as to my logic.
 
Hi all,
27482 said:
how do you explain that in tank C (where this increase of H+ ions should happen and thus pH should drop) this does not happen"? This seems strange to me and contradictory to your description as well as to my logic.
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You need @_Maq_ to answer.

I'm going to guess that the pH values for "C - aquasoil" are likely to be accurate, partially because the water is "saltier" in that treatment.

He isn't adding any alkalinity in the remineralisation.
_Maq_ said:
WATER & MINERALIZATION:
RODI water mineralized as follows will be used without any alterations for the whole experiment in all the tanks:
1696591754641.png
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cheers Darrel
 
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27482 said:
how do you explain that in tank C (where this increase of H+ ions should happen and thus pH should drop) this does not happen"? This seems strange to me and contradictory to your description as well as to my logic.
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I can only guess. From what I know about clays in general, they tend to prefer some cations on exchanging positions. These preferences are then "violated" by external conditions, notably by availability of various cations in the surrounding environment, and pH. So, their preferences do not follow linear functions, it's more complicated.
Let's suppose that with decreasing pH, which means increasing concentration of protons in the surrounding water, the clay is less inclined to release protons (even more protons in the water). It is quite possible that it would still release more protons IF there were higher concentrations of bivalent cations (Mg & Ca) in the water. Possibly. As we know, I've opted for sparingly mineralized water, so the urge to accept calcium and magnesium (and thus: release protons) is nearly exhausted and pH stabilized at given level.
ADA says if should buffer pH at about 6.5. In this experiment, we observe rather 5.6. Possibly ADA expects majority of hobbyists pouring hard tap water into their tanks. That's why higher pH. But the principle, i.e. the buffering capacity of clays, seems to be valid.

By the way, some resins work similarly. We know resins which uptake nitrates and release chlorides in their stead. That's a resin with anion exchange capacity which prefers nitrates over chlorides. Once it's saturated, we can regenerate it in brine, strong NaCl solution. There, the resin takes up chlorides and releases nitrates, because the concentration of chlorides is extremely high. After regeneration, we insert the resin back into our filters and the cycle repeats itself - the resin releases chlorides and takes nitrates.
I think ADA employed similar treatment with some selected clay. They've created clay 'supercharged' with protons by treating ordinary clay with a strong acid. The clay released metallic cations and accepted protons in their stead. That's why the clay can work as a proton donor in less than strongly acidic environment.
 
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Day 37 (Jan 13): dosing iron 8.4 µg/L.
Day 38 (Jan 14): measuring.
1705406346135.png
I'm a bit worried about pH decrease in tank D. On the other side, it's a convenient opportunity to check plants' tolerance to this. So far, they seem to be ok.
Day 39 (Jan 15): water change 50 % with remineralization.
 
Day 40 (Jan 16): photographing.
A(040).jpgB(040).jpgC(040).jpgD(040).jpg
Not much interesting stuff to observe except perhaps that all plants are doing reasonably well. If you can observe some irregularities in tops of Ludwigia Meta, that's of mechanical origin, they tend to get sucked into the very outflow of the pump, or "hiding" behind the inflow tube.
Ammannias do expose something. This genus is prone to stunting (above all, A. pedicellata Gold), and I haven't yet identified the reason. Have a look at the pics:
A(040)a.jpgB(040)a.jpgC(040)a.jpgD(040)a.jpg
 
nijat11 said:
Yeah aquasoil is nice, but after a year it gonna be the same as gravel and we will need root tabs again.
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I don't think it'll ever be like gravel, it remains a nutrient store for a lot longer than that - I'd have thought its CEC would constantly remain in flux, particularly in a very softwater tank like this, but for sure it won't continue to deliver the levels of nutrients it does when new, and so would need to be supplemented with increased water column dosing if the initial dosing is very lean.

I think the plant health indicates the levels of additional nutrients the plants are receiving currently - both at the roots, and leached into the water column - over the apparent lean dosing in the other tanks (though we don't know what's in the secret tank D - lets call it the 'Sheep S#@t Tank' 😂)

I also think we have to take into account the fairly significant variation in light levels that the plants are being exposed to due to reflections from the substrate. The aquasoil tank is noticeably less 'bright', and the combination of lower overall light exposure and higher nutrient levels could be limiting the chance of deficiencies in that tank, and giving the plants an easier ride.
 
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The Ammannias look far the best in the aqua soil (C). And I think overall the plants in (C) look the best - the contrasting effect of the dark soil should not be underestimated however. Also internal reflection and ultimately the amount of light the plants get is a bit higher in the tanks with brighter substrate. Personally I am not fan of the look of this bright whiteish silica sand btw. I think it makes the plants look dull... of course its mostly an aesthetical consideration.

Without drawing any hard conclusions, what this suggest at least tentatively is that the initial boost from mainly TAN (NH4 in particular) when establishing the plants is beneficial - the Aqua Soil tank as of Jan. 2 still measure 10 times the TAN compared to the other tanks. What will happen when the soil is eventually depleted (went from a TAN level of 325 to 155 uM in about 20 days... if thats the half-life it should last no more than 6 months as a source?) only time can tell, but I think the head-start is probably sustainable for quite a while.

Also interesting that the very high levels of NH4 in (C) is not causing any excess in algae.... that is sometime we have discussed before.

For 2nd place I would say its a toss up between the A,B,D ... wow, yes, D's pH is very low.

Cheers,
Michael
 
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Hi @_Maq_ I wonder if an initial high(er) dose of NH4 with (cheap) plain silica sand would more or less yield the same result as using (expensive) aqua soil. In addition to NH4, what else will aqua soil provide?

Would like to hear your thoughts on this.

Cheers,
Michael
 
Wookii said:
unless the dark soil is creating better contrast for the photo. Is that the case viewing them in person @_Maq_ ?
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Even when viewing in person, the comparison is somehow tricky. What strikes me (and you probably can't see) is the clarity of water in tank C. Tank A is also very clear, while tanks B and D not so much.
MichaelJ said:
The Ammannias look far the best in the aqua soil (C).
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Yes, they do. But they show no deficiency in D, as well. And in A, there have been strong signs of some problem (probably iron) but the tops now look promising. For unknown reasons, in tank B Ammannias are stunting.
MichaelJ said:
Hi @_Maq_ I wonder if an initial high(er) dose of NH4 with (cheap) plain silica sand would more or less yield the same result as using (expensive) aqua soil. In addition to NH4, what else will aqua soil provide?

Would like to hear your thoughts on this.
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I rather think not. Maybe you can recall I have made some tests comparing high/low dosing and the results were less than persuasive. I tend to believe the benefits of aquasoil have more to do with general physico-chemical properties. Clays, humic substances, their adsorption qualities, improved root creation... I can only guess.
But you, guys, don't be too focused on Ammannias. If you ask me, I agree, yes, on the whole, tank C is leading the crowd. But by insignificant margin. We've got ten species here, mostly quite demanding ones, and they are doing well, with very minor exceptions. That's a feat in itself, I think. Aquasoil is perhaps 5 % better, but we should not forget about the remaining 95 %! There's not much to invent on plain silica sand, but given the moderate lighting, no CO2 enhancement, it's the water flow (quite intensive) and namely the water composition which should draw your attention, I believe. Don't you think so?
Anyway, the test is not closed, yet, and we shall see (and know) more, perhaps, in upcoming weeks.
Wookii said:
(though we don't know what's in the secret tank D - lets call it the 'Sheep S#@t Tank' 😂)
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Not secret any more.
Happi said:
what are the NO3 levels on all the tanks? I apologize if I have missed this information somewhere.
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0.5 mg/L.
 
_Maq_ said:
We've got ten species here, mostly quite demanding ones, and they are doing well, with very minor exceptions. That's a feat in itself, I think.
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Have to agree with that, the fact you can grow some of the plants on that list low tech is certainly an eye opener to me.
I doff my cap to you sir.

@_Maq_ the Nitrate level in tank C is surely higher than 0.5 mg/L
 
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