Fun with water chemistry, Pt. 1,500...


We talk about a lot of the environmental benefits of botanicals and leaves and stuff. I've went on and on and on about the way a bunch of botanical materials in your aquarium can help foster a diverse and vibrant "microbiome." I think that this ability to foster such a population of organisms within the aquarium may be the top benefit of this approach.

Nonetheless, we receive a lot of questions on various water chemistry topics. Stuff that, although less exciting to me, is important for us to have at least a rudimentary working knowledge of as we venture into the realm of lower pH and tinted water, right?

Admittedly, I've spent a lot less time talking about the chemical benefits of utilizing botanicals in our tanks. Largely, it's because my limited understanding of chemistry is far less than my limited understanding of biology! And it's hard to explain some of this stuff coherently with that "handicap."

Nonetheless, I have been able to do a fair amount of research on some chemistry topics related to our botanical-style aquarium obsession. There's a lot of good academic stuff out there, if you care to dig and study. Let's tackle a couple of topics which come up frequently in discussion with other botanical-style aquairum geeks...

Let's start with "humic substances", okay?

One of the buzzy "catch words" we use a lot is "humic substances." What exactly are those, and why should you even care about them?

I mean, you probably just want to sit back and watch your tank fro ma comfy perch, not ponder the mysteries of water chemistry, right? I can't say that I blame you, but it IS kind of cool to learn a bit about this stuff.

Let's get to it really quickly, and you can get back to your coffee...

"Humic substances" are produced by biodegradation of plant and/or animal materials. Does that include botanicals and leaves? From everything I can find, it does.

Typical humic substances fall into three categories: humic acids, fulvic acids, and Humin (carbon-based "macromolecular substances" found in soils). I know, your head is already spinning. Interestingly, humic acids are insoluble in water with an acidic pH. Fulvic acids, on the other hand, which are also derived from humic substances, are soluable in water under a wide range of pH levels.

Confused yet?

I am. But that's really nothing new...

Up until the last decade, science considered any influence of humic substances on aquatic life as “anecdotal”. However, a lot of research conducted within the last decade or so has demonstrated that humic substances have an important direct physiological influence on aquatic life, including of course, fishes! In extreme blackwater conditions, they are known to be what makes it possible for fishes to survive in pH as low as 3.9!

In less extreme conditions, we are just now beginning to understand the role they play. However, they have been documented to play a major role in the functionality of a fish’s immune system, influence growth, improve lifespan, prevention of oxidative DNA damage, detoxification of heavy metals and organic pollutants, suppression of cyanobacteria, regulation of gill function, protection of fish from environmental physiological stress (low oxygen levels, temperature swings, pH shifts, TDS changes, Ammonia, Nitrite, etc…) and faster recovery from these environmental stressors.

Humic substances have also proven to possess antifungal, antiparastic, and antibacterial properties, inhibiting the growth of  nasties, like Aeromonas hydrophila, A. sobria, and Escherichia coli, just to name drop a few.

You can do a lot more research on this stuff if you're willing to dig a bit. I do recommend that, if you're interested.  

Another question we get a lot is about the "water-softening capability of botanicals", to which I respond almost reflexively, "There is none." However, it is known that our old and controversial friend,  peat moss, has demonstrated some capacity to conduct ion exchange ( a process in which which unwanted dissolved ions in water are exchanged for other ions with a similar charge.) Ions are atoms or molecules containing a total number of electrons that are not equal to the total number of protons.

Peat softens water by exchanging humic acids for magnesium and calcium.

It's actually true.

Peat effectively binds calcium and magnesium ions, while simultaneously releasing tannic and other acids into the water. These acids "work" the bicarbonates in the water, reducing the carbonate hardness and pH to some extent. And it will tint the water, as well!

Interesting, right? However, you can't just drop some peat into your tank and expect "Instant Amazon." This process requires "active peat filtration" (the water passing over over the peat itself) to make this happen. 

Now, of course, being the curious and occasionally reckless fish geek that I am, I played around with this idea once, to try to see if this does, indeed work.

And, well, it does sort of work.

It took a shitload of peat and a fair amount of time to reduce my Los Angeles tap water, with hardness exceeding ~240ppm and ph of 8.4 down to "workable parameters" of 6.4ph and a hardness level of around 40ppm. How much are we talking? It took a full  2-cubic-foot bag of peat, added to  a 30-gallon plastic trash can, filled with with my tap water, over 8 days in order to achieve these parameters.

So, yeah. The idea does work. Is it efficient?

Um, not in my humble opinion.

By comparison, my SpectraPure 4 stage RO/DI unit cranks out 80+ gallons of zero TDS, zero carbonate hardness water in a day. Now, one could argue that the rejection rate of RO/DI makes it less efficient- but hell, I water my garden with the reject water! And yeah, a unit like mine retails for around $300 plus USD, more than a 2-cubic foot bag of peat, but the long-term, consistent efficiency  and reliability is pretty obvious to me. All in all, for maximum efficiency, consistency, and control, just invest in an RO/DI unit and you'll create soft water with little effort and no mess.

Yeah, it IS a bit pricy to purchase an RO/DI unit, but well worth it.

But yes, you CAN soften water with peat to some extent if you're put to it, have the means to do it, and test. I've long ago lost that thrill that some people get from these types of "money-saving DIY" methods. To me, I simply decided to forgo other indulgences, save my money for a while, and invest in  the RO/DI unit and call it a day.

You should, too.

Okay, well that's a quick summary on a couple of "water chemistry" topics that come up frequently around here. No doubt, as we have in the past, we'll continue to tackle others. 

We welcome your stories, input, and suggestions in this wide-open, yet well-trodden arena within the hobby.

In the mean time, I'm going to expend more effort on studying decomposing leaves, sediments, and the microbiome they support...'cause I'm that kind of geek. (Besides, it's a bit more exciting to me, lol 😆)

Stay engaged. Stay experimental. Stay curious. Stay bold...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




Scott Fellman
Scott Fellman


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