Micro from tap water

[LMuhlen]

How does KH affect things if we are injecting lots of CO2? I certainly use less CO2 to hit my pH target if I lower the KH to below 10, ideally 8 or 6, though some say 4 or lower. I do it mainly to safe money and bother, if I don't I double my cylinder use over the year.

My understanding is that, for practical applications, changing the KH will change the pH range you work with when injecting CO2, but it won't change the consumption of CO2 in a significant way. Regardless of the KH used, you will have the same ratio of CO2 consumed to CO2 dissolved in water. What changes is the initial and the final pH, which will be higher when the KH is higher, and vice-versa. If you perceive that CO2 consumption increases at different KH levels, you are probably doing something wrong with your pH targets and in fact dissolving more CO2 than what you were before, reaching a higher concentration.

That is assuming that your goal is to reach a given CO2 concentration. If the goal is to reach a given pH to affect how the nutrients react in water, then yes, you'll need more CO2 to get that same pH when the KH is higher. But it sounds unusual to use CO2 to adjust the pH, it is indeed better to adjust alkalinity and keep CO2 in a range that is good for whatever you expect from your plants and safe enough for livestock.

 

[Connswater]

reach a given CO2 concentration. If the goal is to reach a given pH

I think I am at both, simply because I have such hard tap water. And, I refuse to go down the RO route and then remineralise. And with hard water even modest water changes can make a big difference. I struggle to achieve my desired KH, and then I want to hit 20-30 ppm of CO2 for plant supply - I do get vigorous pearling, I know disapproved of by many here - but I also want to make sure that nutrients are readily available - but I am also no chemist, and I'm my own worst enemy. And I'm not above helping the fish out at night with surface agitation, CO2 lost.
Limited range of crypts and hornwort and tap water, plenty of light and sequestered Iron and all was fine in the past, just a bit limited. Livebearers were easier.

 

[ElleDee]

Here I would beg to differ slightly. What @ElleDee writes is true for terrestrial plants, but apparently not for aquatic plants. In an aquatic environment, the acids secreted by the roots would immediately become so diluted that they would not be effective enough. Flooded sediments generally have a very low redox (as low as -150 mV at a depth of 2 cm, and even -250 mV at 10 cm - see Modification of sediment redox potential by three contrasting macrophytes: implications for phosphorus adsorption/desorption). With such a low redox, the oxidised iron and manganese are rapidly and abundantly reduced and thus transferred back into the soil solution, where they are available to plants. Not only that, but the iron and manganese in this soil solution can be so high as a result of this reduction that plants are often at risk of poisoning (toxicity). Thus, in flooded sediments, iron and manganese are unlikely to be deficient; rather, they are toxic. Plants counteract this excess by excreting oxygen from their roots. This results in the oxidation of the reduced iron (and manganese), which often results in a rusty colour of the roots (called „iron plaque“ => Iron plaque formation on roots of wetland plants).

You are right that aquatic and terrestrial roots do not always function the same, but you inspired me to do a little research and this recent article (The Status of Research on the Root Exudates of Submerged Plants and Their Effects on Aquatic Organisms) indicates that some aquatic plants do use organic acids to increase availability of nutrients. Not that they don't also release oxygen as you said - there's a lot going on. It seems it depends a lot on the environment and there are significant differences between species. I am not an expert on this topic, but while I might not understand exactly what all is going on in the substrate, if I let my plants root in well they can deploy the appropriate adaptive measures and they do better than if I rely on the water column for everything.

As an aside, I do wish we had better data on stuff like substrate redox in a planted aquarium and the flux of nutrients, etc. between the substrate and water column. I've heard a lot of opposing takes, but I've not really been convinced about anything. Alas, studies on natural systems can only get you so far.

Good stuff, thanks for bringing that up.

 

[dw1305]

Hi all,

I'm curious about the chelation methods used for this product and the other products on the website. I assume they use Amino based Chelation?

I must admit I don't know, I'll see if I can find out.

cheers Darrel

 

[Teleos]

What are the usual values for trace elements in tap water?
The water data for my tap water is somewhat incomplete. There is only data for B, Cu, Fe and Mn. Nothing about Zn, Mo.
B = 0.1 mg/l
Cu = 0.00001 mg/l
Fe = 0.02 mg/l
Mn = 0.005 mg/l

I do not assume that toxic levels of trace elements can be reached in an aquarium. Unless you use large quantities of garden soil or similar as substrate. Or am I wrong?

 

[Marcel G]

This recent article (The Status of Research on the Root Exudates of Submerged Plants and Their Effects on Aquatic Organisms) indicates that some aquatic plants do use organic acids to increase availability of nutrients ...

Great job, @ElleDee! Thank you very much for this article! This table in it is especially interesting (and summarizing):

 

[ElleDee]

Great job, @ElleDee! Thank you very much for this article! This table in it is especially interesting (and summarizing):
View attachment 225040

Happy to help, @Marcel G! I am still working through it myself, but it's been a great read so far. It was nice to find something that was comprehensive and relevant to the hobby for once - usually it's one or the other.

 

[Marcel G]

And yet, are trace elements from tap water available to plants?

I apologize to you, @Genahanney, for the slight digression from the topic, which resulted in developing the discussion in a somewhat different (for you probably rather undesirable) direction. It was probably best answered by @Happi in post #30. The microelements that are in the water will be there (with a few exceptions) oxidized, thus inaccessible to the plants. If you wanted to convert them to an accessible form, you would have to ensure their "deoxidation" aka reduction. You would only be able to do this to some extent by radically lowering the pH (well below 6) or by adding chelates. When the element is released from the chelate, it will be oxidized within a few minutes or hours at most (but the plants may be able to take some of it before this happen). Therefore, I think that far better than relying on the availability of microelements in tap water is to either (1) add them to the aquarium water in chelated form, or (2) use an organic substrate (like Aquasoil or similar, such as garden soil) that has all the microelements in abundance and that the plants can extract from it (as opposed to the water column) when needed.

Edit: You can think of chelate as a ball of dough with raisins (= microelements). If you drop it in water, the dough will gradually break down and the raisins will gradually (= one by one) release from it. Immediately after release, the raisin starts to harden until it becomes a stone (= inaccessible nutrient). But before this happens, the plants have time to bite off some of the nutrients from the raisin. After a while, another raisin falls out of the dough, and the whole process repeats.

 

[dw1305]

Hi all,

to do a little research and this recent article (The Status of Research on the Root Exudates of Submerged Plants and Their Effects on Aquatic Organisms) indicates that some aquatic plants do use organic acids to increase availability of nutrients. Not that they don't also release oxygen as you said - there's a lot going on.

Great job, @ElleDee! Thank you very much for this article!

@ElleDee that is fantastic and has certainly fleshed out:

I think aquatic plants are still altering the composition of the rhizosphere microbiome to facilitate nutrient uptake, basically roots are just leaky structures.

I'm definitely going to refer people to @Happi's thread when this comes up again as topic.

It was probably best answered by @Happi in post #30.

It is just a perfect answer.

cheers Darrel

 

[dw1305]

Hi all,

I assume they use Amino based Chelation?

It looks likely, I couldn't find anything specific, other than this patent <"CN104119146A - Phosphorus fertilizer containing amino acids and preparation method of phosphorus fertilizer - Google Patents">.

I've never found any need to <"add phosphate (PO4---) as anything other than a simple salt">, so I don't have any practical experience of other compounds. I may just have failed to <"recognise phosphorus deficiency">, but I think that is more unlikely.

<"Polyphosphate"> might be another option, so not strictly chelation.

cheers Darrel