Plants And Water Chemistry

As I understand it, it takes a super dense plant cover for an aquarium to have its water chemistry affected (in particular the three nitrogenous compounds central to our hobby). However, I was just wondering if someone can give me a brief lesson on biochemistry as to what nutrient from the water do plants really take?

I've generally read about plants taking up nitrates most of the time. Some also say they suck more ammonia out of the water more than they do nitrate. Haven't heard much on what they do with nitrite (or if they do anything with it). Also do plants absorb lots of metals in comparison to those nitrogenous compounds? All those fertilizers are largely made of metals like copper and magnesium so it kind of makes me think about it.

 

People talk about plants eating nitrate because that's the thing they think they should see in their water tests that they don't see. But most aquarium plants actually suck up the ammonia in the tank before it can even become nitrite. I've not found that especially dense planting is needed to get this result. If you look into the Walstad tank method, you'll get a lot more scientific explanation, but that is the jist of it.

 

I see. Isn't a pretty dense planting is one prerequisite for the Walstad tank? I guess I better find a copy of Walstad's original book to get a better idea about this.

 

I LOVE aquarium chemistry I've bookmarked some really good articles about this. OP, more macro nutrients like nitrogen, phosphorus, and potassium are taken up than micro nutrient heavy metals. However, alkaline earth metals such as magnesium and calcium are also very important.
I'd also like to share something I've been researching for a while.
These require some basic chemistry knowledge, but definitely aren't beyond the realm of understanding

Let's start off by saying an organic molecule or compound is defined as carrying a carbon (C) atom. Since our typical plant fertilizers such as ammonia (NH4+) and nitrate (NO3-) do not contain a C, they are inorganic.


Plant and Soil Sciences eLibrary

Particularly:
"Ammonium (NH4+) and nitrate (NO3–) are the predominate inorganic forms of nitrogen in soils. Ammonium exists in exchangeable and nonexchangeable forms. Nitrite (NO2) and nitrous oxide (N2O) are present in soil in lesser quantities. Plants normally use nitrogen in only the ammonium and nitrate forms. Nitrite is actually toxic to plants."


And:



Particularly:
"Nitrogen can also become available for plant use from organic N sources. But first these organic sources must be converted to inorganic forms before they are available to plants."

"Nitrogen exists in crop residues in complex organic forms and the residue must decay (a process that can take several years) before N is made available for plant use."

"In considering the many transformations and reactions of N in soils, there are some major points to keep in mind. Although N can be added to soil in either organic or inorganic forms, plants take up only inorganic N (that is NO3--N and NH4+-N)."


And:

https://chem.libretexts.org/Textbook_Maps/General_Chemistry_Textbook_Maps/Map:_ChemPRIME_(Moore_et_al.)/08Properties_of_Organic_Compounds_.../8.18:_Organic_Nitrogen_Compounds

Particularly:
"There is a tremendous variety of organic compounds which can be derived from carbon, hydrogen, and oxygen..."

"Amines may be derived from ammonia by replacing one, two, or all three hydrogens with alkyl groups."

"Amines usually have unpleasant odors, smelling “fishy". The three methylamines listed above can all be isolated from herring brine. Amines, as well as ammonia, are produced by decomposition of nitrogen-containing compounds when a living organism dies."


And:



Particularly:
"When plant residues are returned to the soil, various organic compounds undergo decomposition. Decomposition is a biological process that includes the physical breakdown and biochemical transformation of complex organic molecules of dead material into simpler organic and inorganic molecules (Juma, 1998)... Carbon cycling is the continuous transformation of organic and inorganic carbon compounds by plants and micro- and macro-organisms between the soil, plants and the atmosphere"

https://www.yorku.ca/spk/fishbiol09/FB09lecture11.pdf

Everything here can be applied to our hobby.


At this point you're probably thinking, okay Mak, but what does all this chemistry mumbo jumbo mean?

It means: When one of our fish dies, when food decomposes, when whatever waste decomposes in our tanks, it doesn't just "produce ammonia." Ammonia is a blanket term often repeated in this hobby. A lot of organic C containing compounds are also present during decomposition in our tanks. However, plants cannot just "take up" that waste! Plants don't use organic nitrogen compounds. Bacteria must first convert those organic compounds into our inorganic compounds. This highlights the importance of a good substrate in planted tanks that allows bacteria to thrive. It also tells you that you cannot just rely on plants to clean your tank. If your bacteria load has not been fully established, the plants will not clean up that decomposing fish for you. Cycling does include establishing your filter, but in planted tanks it also means you must allow additional bacteria to grow that will convert organic compounds to inorganic ones.
Disclaimer: I'm not a biochemist, all information I've just written is a summary of my research. I have not studied this in a professional setting so please correct me if I'm wrong about something

Sorry for the essay, but I hope this was able to bring some important information to everyone. Plants help your tank, but only when you help the plants.

 

Lol that must have taken a while to write but wow what an exciting read! Thanks Mak for reviewing the relevant literature and nerding along with me on this topic. While biochemistry is not my academic cup of tea in general, this definitely is something I'd love to know more about given its relevance to our hobby.

 

Lol that must have taken a while to write but wow what an exciting read! Thanks Mak for reviewing the relevant literature and nerding along with me on this topic. While biochemistry is not my academic cup of tea in general, this definitely is something I'd love to know more about given its relevance to our hobby.

Thank you! And I couldn't agree more. The hobby has made me really interested in chemistry, while I used to detest it.

 

-Mak- great info...

Love the hobby, still hate chemistry...

Also of note is with ferts, how they work together, not separately... p affects k affects n, mg affects iron uptake, etc... I will try to find the articles I can across that made it so much easier to understand ferts and dosing... they are all part of the balance...

 

I see. Isn't a pretty dense planting is one prerequisite for the Walstad tank? I guess I better find a copy of Walstad's original book to get a better idea about this.

You can do tanks inspired by her method without potting soil, which would mean less dense planting. Unless you have a high bioload, of course. It's all a balancing act of nutrient to plant.

Also, reading her book is great (I'm pretty sure she's made it available for free online) but also, she was a frequent poster on one of the online plant forums and they actually have a whole sub-forum dedicated to her method. I'll see if I can find it later but I'm pretty sure it was theplantedtank.

 

This is something I've also become interested in lately... I was interested when I grew orchids for years... but aquatic plants use nutrients in a much more informative way - as in, you can measure what they take from the atmosphere around them ~ i.e. water ~ (unlike terrestrial plants)... anywho... I'm following! I am interested in what everyone has to say in this subject.

Only thing I had to add has already been added: plants soak up calcium & magnesium or basically more or less your GH as well... I've noticed this in my own tanks. Because I have no KH or GH out of the tap to speak of, I know what I add ~ calcium, magnesium (although with magnesium, I'm not 100% sure on dosage.. so that's not consistent - just added a handful of times) & aragonite sand etc ~ and I know that it is depleted on a regular basis exactly the same way the (complete) ferts I add are depleted. Which is why this subject/question piqued my interest thanks for starting this discussion!!

Edited to add: I thought Diana Walstad was on aquaticplantcentral... maybe I'm wrong? Probably should've looked before saying this? Not that plantedtank wouldn't, but there certainly is a forum that is more dedicated to her than most... ?

 

I was wrong, it is APC that Diana Walstad uses. The link to the forum is below:
El Natural - Aquatic Plant Central

Diana's name is Dwalstad on the forum. She has many posts in the forum about her tank method, but I don't know that she is active on there anymore.

 

I was wrong, it is APC that Diana Walstad uses. The link to the forum is below:
El Natural - Aquatic Plant Central

Diana's name is Dwalstad on the forum. She has many posts in the forum about her tank method, but I don't know that she is active on there anymore.

Yea.... I was under the impression she wasn't active on the forum anymore either... which is really too bad! I have definitely gone back and read old threads that she took part in/commented in (yes, one of the only times I actually could've almost been considered a stalker! ops: I just like to learn from knowledgeable people! Lol:shy isn't she from NC? (I am too, which is another reason I took interest haha.. gonna stop now... before I sound too creepy haha! Omg!)

I find this subject so interesting, and I am truly happy to see that I'm not the only one! Lol... Plant Geek Club right here y'all!

Also, thanks for her username.. I couldn't remember what it was. Hopefully I can remember it for when I require information from the vault of knowledge that is Diana Walstad!

 

Jocelyn Adelman speaking of ferts, I also found a study that relates ph to nutrient uptake:

https://ian.umces.edu/pdfs/crossley_2002_thesis.pdf

I doubt anyone will actually read the entire thing (I haven't) but it looks pretty good. This chart sums up ph vs nutrient uptake:

 

Mak nutrient uptake in specific pH would also depend highly on the type of plant, and the nutrients it uses, and whether it prefers acidic soil or calcium-rich soil...

The list goes on and on. We could study this subject for years and still not fully understand it.

 

I LOVE aquarium chemistry I've bookmarked some really good articles about this. OP, more macro nutrients like nitrogen, phosphorus, and potassium are taken up than micro nutrient heavy metals. However, alkaline earth metals such as magnesium and calcium are also very important.
I'd also like to share something I've been researching for a while.
These require some basic chemistry knowledge, but definitely aren't beyond the realm of understanding

Let's start off by saying an organic molecule or compound is defined as carrying a carbon (C) atom. Since our typical plant fertilizers such as ammonia (NH4+) and nitrate (NO3-) do not contain a C, they are inorganic.


Plant and Soil Sciences eLibrary

Particularly:
"Ammonium (NH4+) and nitrate (NO3–) are the predominate inorganic forms of nitrogen in soils. Ammonium exists in exchangeable and nonexchangeable forms. Nitrite (NO2) and nitrous oxide (N2O) are present in soil in lesser quantities. Plants normally use nitrogen in only the ammonium and nitrate forms. Nitrite is actually toxic to plants."


And:



Particularly:
"Nitrogen can also become available for plant use from organic N sources. But first these organic sources must be converted to inorganic forms before they are available to plants."

"Nitrogen exists in crop residues in complex organic forms and the residue must decay (a process that can take several years) before N is made available for plant use."

"In considering the many transformations and reactions of N in soils, there are some major points to keep in mind. Although N can be added to soil in either organic or inorganic forms, plants take up only inorganic N (that is NO3--N and NH4+-N)."


And:

https://chem.libretexts.org/Textbook_Maps/General_Chemistry_Textbook_Maps/Map:_ChemPRIME_(Moore_et_al.)/08Properties_of_Organic_Compounds_.../8.18:_Organic_Nitrogen_Compounds

Particularly:
"There is a tremendous variety of organic compounds which can be derived from carbon, hydrogen, and oxygen..."

"Amines may be derived from ammonia by replacing one, two, or all three hydrogens with alkyl groups."

"Amines usually have unpleasant odors, smelling “fishy". The three methylamines listed above can all be isolated from herring brine. Amines, as well as ammonia, are produced by decomposition of nitrogen-containing compounds when a living organism dies."


And:



Particularly:
"When plant residues are returned to the soil, various organic compounds undergo decomposition. Decomposition is a biological process that includes the physical breakdown and biochemical transformation of complex organic molecules of dead material into simpler organic and inorganic molecules (Juma, 1998)... Carbon cycling is the continuous transformation of organic and inorganic carbon compounds by plants and micro- and macro-organisms between the soil, plants and the atmosphere"

https://www.yorku.ca/spk/fishbiol09/FB09lecture11.pdf

Everything here can be applied to our hobby.


At this point you're probably thinking, okay Mak, but what does all this chemistry mumbo jumbo mean?

It means: When one of our fish dies, when food decomposes, when whatever waste decomposes in our tanks, it doesn't just "produce ammonia." Ammonia is a blanket term often repeated in this hobby. A lot of organic C containing compounds are also present during decomposition in our tanks. However, plants cannot just "take up" that waste! Plants don't use organic nitrogen compounds. Bacteria must first convert those organic compounds into our inorganic compounds. This highlights the importance of a good substrate in planted tanks that allows bacteria to thrive. It also tells you that you cannot just rely on plants to clean your tank. If your bacteria load has not been fully established, the plants will not clean up that decomposing fish for you. Cycling does include establishing your filter, but in planted tanks it also means you must allow additional bacteria to grow that will convert organic compounds to inorganic ones.
Disclaimer: I am a high school student and not a biochemist, all information I've just written is a summary of my research. I have not studied this in a professional setting so please correct me if I'm wrong about something

Sorry for the essay, but I hope this was able to bring some important information to everyone. Plants help your tank, but only when you help the plants.

Please let me use this!! Can I copy it? I am building an article up about this very subject and this is gold!

 

Please let me use this!! Can I copy it? I am building an article up about this very subject and this is gold!

Absolutely! Please link it to me once you're done, I'd love to see!

 

Absolutely! Please link it to me once you're done, I'd love to see!

Absolutely! Please link it to me once you're done, I'd love to see!

YYYAAASSSS!!! And for sure! Will keep ya posted when I get it developed!