Tannic, Humic, Fluvic, etc.

[TCMontium]

Hello,

I apologize beforehand if these questions were answered many times previously in these forums or other aquatic websites. Maybe I just couldn't find the right keywords to find any of those threads and articles. My questions are:

- Since the Amazon Basin water (especially blackwater habitats) mostly contains humic acids and the leaves we use usually release tannic acids, is using lots of dead leaf material really healthy for Amazon Basin species (blackwater species in particular)?
I am asking this mostly because there are many articles about tannic acid usage on commercial fish eggs and sometimes tannic acids seem to be harmful for hatch rate (or maybe I'm just misinterpreting the data).

- Is there a humic acid product that you use or heard is very effective for creating blackwater acidic conditions? Or is mined peat moss only product you know of?

- Is there a crucial difference between fulvic acid (the type of humic acid in peat moss, I believe, at least Sera Super Peat says so) and humic acids naturally found in Rio Negro and similar rivers?

 

[gerald]

I was under the impression that most all decaying tree leaves release a blend of humic, tannic, and fulvic acids, and that blackwater habitats contain all three types, but I have never looked into the details or differences between organic acids in terms of their significance to fish. ... Following along to see what other folks here can teach us ....

from Wikipedia: "Fulvic acid is created in extremely small quantities under the influence of millions of useful microbes, working on the decay of plant matter in a soil environment with sufficient oxygen. ... Analytical quantification methods in the past measured both humic and fulvic acid as one substance. This created analytical challenges and mass confusion for those products that are fulvic isolates, having no measurable or very low humic acid in them. It is also the primary reason that fulvic acid content claims were usually inaccurate and much higher than is being brought to light with the new standardized method."

The fish-related references i've seen just lump them all together as "DOC" (dissolved organic carbon). I'm not sure anybody has yet tried to distinguish their different roles as they pertain to fish health.

 

[ButtNekkid]

Hi,

I remember reading one study that claimed that some higher concentrations can be harmful to larvae development and/or hatch rate.
I have read two scientific studies that stated that some commercial blackwater products don´t provide the same benefits as natural substances.

Some good info:
https://tanninaquatics.com/blogs/the-tint-1/humic-substances-in-freshwater-aquariums

 

[TCMontium]

I will interrupt my own thread, but I didn't understand this sentence in the link at all: "Yes, peat softens water by exchanging humic acids for magnesium and calcium but this requires active peat filtration (the water running over the peat itself). The resulting “tea” itself has no such properties."
So… peat releases humic substances to water, but if you add that water to your aquarium, it doesn't? What? Maybe I'm just confused because English isn't my mother language.

The scientific resources part of the link seems very useful and probably (hopefully) has the answers to most of my questions. I have to read those articles some time.

 

[Bart Hazes]

I don't think that is written correctly. What I think they mean is that peat, the physical material, can act as a cation-exchanger, just like the ion exchange resins you can buy for your RODI "reverse osmosis deionised" setup. Basically the peat has negatively charged groups that weakly bind monovalent (1+) metal cations or protons. Magnesium, calcium or other multivalent metal ions bind more tightly and get captured by the peat while displacing monovalent ions. The magnesium and calcium are now 'locked up' and no longer bioavailable.
The peat tea is soluble, so even if it binds multivalent cations the ions remain in solution.

 

[gerald]

What Bart says. It's mainly the peat fibers that bind up Ca and Mg ions, not the organic acids. Adding "blackwater tonic" or peat extract won't soften the water.

 

[dw1305]

Hi all,

I will interrupt my own thread, but I didn't understand this sentence in the link at all: "Yes, peat softens water by exchanging humic acids for magnesium and calcium but this requires active peat filtration (the water running over the peat itself). The resulting “tea” itself has no such properties."
So… peat releases humic substances to water, but if you add that water to your aquarium, it doesn't? What? Maybe I'm just confused because English isn't my mother language.

The scientific resources part of the link seems very useful and probably (hopefully) has the answers to most of my questions. I have to read those articles some time.

Yes, like @Bart Hazes and @Gerald have said the first bit is wrong and there are two different processes occurring. The humic and fulvid compounds are are chelators and the "sphagnan" in sphagnum peat works via ion exchange. Because sphagnum peat is harvested from ombrothophic (rain-fed) mires, all the <"initial cation exchange sites"> are occupied by a proton (H+ ion).

Have a look at @regani's comments in <"700 liter Amazone..."> and this link <"the ecology of Sphagnum">:

......A growing Sphagnum plant is continuously creating sites at which this exchange of ions can take place and the major active substances at those ion exchange sites are uronic acids, which constitute 10-30% of the dry mass in Sphagnum. The uronic acids are held in the cell walls as a polymer, commonly referred to as sphagnan. Sphagnum plants also contain a variety of phenolic compounds. There is evidence that uronic acids are responsible for ion exchange at low pH levels, with the phenolic compounds working at higher pH levels. In Sphagnum plants the concentrations of the phenolic compounds are lower than those of the uronic acids......

cheers Darrel

 

[gerald]

Does that mean peat extract (without the plant fibers) can still lower the GH hardness by chelating Ca+Mg ions, even though it's not actually removing any ions by ion exchange? If so, then my statement above "peat extract won't soften the water" may be wrong.

 

[dw1305]

Hi all,

Does that mean peat extract (without the plant fibers) can still lower the GH hardness by chelating Ca+Mg ions, even though it's not actually removing any ions by ion exchange?

I think it probably does.

The addition of citric acid (C6H8O7) lowers conductivity (but not a lot), which must be via chelation.

@regani talks about the mechanism in <"peat granules...">.

cheers Darrel

 

[blakemarkwell]

Fulvic acid (the most well known and active one in the water column at acidic pH) contain many carboxylic acid groups which act as chelators for a variety of multivalent ions, including divalent calcium and magnesium. And yes, citric acid has chelation properties too using the same functional groups as fulvic acid.