A certain (water) quality...

There is a certain mystery surrounding the idea of blackwater, botanical-style aquariums. A lot of misunderstanding, misinterpretations, and downright confusion floating around out there- much of it put out there by hobbyists who might have never even attempted to keep such an aquarium personally.

And, I admit, our botanical-style aquariums are a bit of an enigma.

I mean, we have tanks with all of this stuff decomposing in the water, yet manage to maintain high water quality and stability for extended periods of time without any real "magic", in terms of procedure or equipment. 

What gives?

Are we just lucky? Or, is there a method to this madness?

Of course, not being a scientist makes it kind of challenging for me to make all kinds of assertions about water quality and chemistry, so I will at least try to focus on what we want to achieve, and what we can measure, water quality-wise, and how botanical-style aquariums seem to be able to "pull it off" given the vast quantities of leaves, seed pods, etc. contained within them.

Of course, observation and testing of water parameters are your two best friends, as they are in any hobby speciality. We kind of have a pretty good "handle" on which tests make the most sense for our pursuits, too. It's a given that ammonia, nitrite, pH and DKH are the key indicators which most hobbyist will want to know about. 

Little needs to be said here on the application,  rationale, and interpretation for utilizing such tests in our aquariums. You can Google that topic and pretty much come up with like  3,000 articles on the topic!


And of course, there are the tests which give us information on the quality of the environment we've created- nitrate and phosphate. These are also very important tests to botanical-style aquarium lovers, as they help us get an understanding of the water quality trends occurring in our tanks.

Nitrate (NO3) is not necessarily considered "toxic" at a specific level, although a typical rule of thumb is to keep readings under 50 mg/l- or better still, 20mg/l or less, for most fishes at various stages of their life cycle.  

Although there is no agreed-upon "lethal dose", as indicated above, and many fishes can tolerate prolonged exposure to up to 500 mg/l of nitrate, studies have revealed that prolonged exposure to elevated levels of nitrate may reduce fishes' immunity, affecting their internal functions and resistance to disease.

Many fishes can adapt- to a certain extent- to a gradual increase in nitrate over time, although long-term physiological damage can occur. And of course, some fishes are much more sensitive to nitrate than others, displaying deteriorating overall health or other symptoms at much lower levels..

One of the interesting things about nitrate is that it can- and will- accumulate and rise over time in the aquarium if insufficient export mechanisms (ie; water exchanges, lack of chemical or biological filtration capacity, etc.) exist within the aquarium. This, of course, gives the impression that fishes are "doing okay" when the reality is that they are exposed to a long-term stressor.

And of course, there are many long-understood approaches to reducing these compounds in aquariums. This is "long-settled" aquarium knowledge, so none of this should be really "new" to you- although it deserves repeating here because it's so fundamentally important to our hobby.

The presence of aquatic plants, long known for their utilization of nitrate as a growth factor, is also considered a viable way to reduce/export nitrates, along with overall good husbandry (ie; stable fish population, proper feeding technique, etc.). In fact, I imagine that with all of the experimentation going on with various aquatic plants in blackwater/botanical-style aquariums, we may simply make the practice of including certain species (say, floating plants or whatever) as a "defacto" part of the nutrient export process in our tanks at some point.

I could see regular pruning and removal of plants as they grow as an easy, effective extension of the nutrient export process, much as we do the same with macro algae in reef aquariums. When you remove plant materials via trimming, you're effectively exporting nutrients from the system permanently.

Of course, even without plants, I have noticed some very interesting long-term trends regarding water quality in my botanical-style aquariums over the years. 

In my botanical-filled, natural-style aquariums, I have personally never observed/measured elevated levels of nitrate. In fact, with a good husbandry regime in place, undetectable (on a hobbyist-grade test kit, at least) levels of nitrate have been the norm for my systems. I think that the highest nitrate reading I've personally recorded in a botanical-style system which I maintained was around 10 mg/l.

Why is this?

Okay, let me speculate a bit, okay?

I think it's about coupling long-trusted husbandry practices with the processes which occur in Nature.

I personally feel that well-maintained systems, including our heavily botanically-influenced ones, offer a significant "medium" for the growth and proliferation of beneficial bacteria species, such as Nitrospira, etc. I have a totally ungrounded "theory" that the presence of botanicals, although in itself a contributor to the the biological load on the aquarium, also is a form of "fuel" to power the nitrification process- a carbon source, if you will, to elevate levels of biological activity in an otherwise well-maintained system. 

Okay, sounds like a lot of cobbled-together "mumbo jumbo", but I think there is something to this.

I mean, when you think about it, a botanically-rich aquarium, with leaves and other materials- fosters the growth of bacteria, fungi, biofilms, and supports crustaceans and other organisms which can consume and metabolize the botanicals as they break down physically, along with fish wastes and other organics which arise as a result of this process.

A sort of "on board" biological filtration system, if you will, with the added benefit that fishes will consume some of these organisms. Perhaps, (and some might say that I'm reaching here a bit) even the basis for a sort of "food web", something that we know exists in all natural aquatic ecosystems.

Something to think about!

I find this among the single most exciting potential benefits of a botanical-style aquarium. In fact, I believe that, once serious scientific study is conducted on this stuff, it may prove to be a foundational component of the botanical-style aquarium. We will embrace the addition and decomposition of natural materials in our aquariums as a sort of "catalyst" to create a stable, productive closed ecosystem, which effectively metabolizes the materials within...

Just like in Nature.

Sure, it may not be the classic definition of "beauty" in the aquarium hobby, but from a functional standpoint, it's magnificent! And yes, I realize that our aquariums, no matter how cool they look and what processes they embrace are not open, natural systems. However, I feel that many of the same processes which occur in Nature are also present in our aquariums, besides just the nitrogen cycle.

Only further research will tell. 

The other measure of water quality that most of us should consider is phosphate (PO4). It's a salt of phosphoric acid- an inorganic chemical. It's an essential chemical for the growth of plants, and other living organisms. Phosphate gets a lot of "bad press" in the hobby-particularly the marine side- as a contributor to the growth and proliferation of algae, which it is.

However, it's really only half of the equation, as algae only grows if nitrogen is also present...And sufficient light, of course. So, it's a contributor to algae issues and overall water quality- not the sole culprit. 

In the reef side of the hobby, phosphate has been vilified as a growth inhibitor to coral, and all manner of additives, reactors, and removal media have been developed to combat it. The reality, IMHO, is that phosphate- although a great measure of overall water quality, tends not to become a problem in an otherwise well-managed aquarium. It gets into our systems in the first place primarily via food, and will accumulate if mechanisms for its absorption/utilization or removal don't exist. 

So, yeah- perform those regular water exchanges. Yet another arguement in favor of them! My head absolutely explodes when I hear hobbyists bragging that they never do water exchanges and that their tank is thriving. WHY in the fuck would you want to do this...and why would you be proud of this completely irresponsible behavior?

Because they are closed aquatic systems, our aquariums can't process 100% of the organic material accumulating in the water. So, when you eschew water exchanges, this stuff is continuing to accumulate, and you're essentially operating on borrowed time before the concentration becomes detrimental to your fishes.

Or, are you? 

I ask this question with all due sincerity.

I mean, could it be that the age-old dream of a "perfectly-balanced aquarium" IS possible- even when what we consider "foundational" husbandry practices are ignored? I couldn't say for certain why "success" comes to people who apparently skirt this basic principle of aquarium keeping. It seems odd that they'd take such a seemingly apathetic approach: Just topping off evaporated water, feeding fishes, replacing filter media, and nothing else.

On the other hand, is there something to it?

Or is this just "dumb luck?" Could it be that they have-perhaps through no deliberate effort of their own (sorry, guys)- achieved some sort of weird "import-export equilibrium", and that the system metabolizes all of the nutrients and trace elements imparted into the water with complete efficiency?

I personally don't thi- Arghh...We'll stop with that here. I could literally debate and theorize this for days...Don't start me! 

I'm not sure if it's the physical process of doing these water exchanges, but a lot of hobbyists just hate doing them. Like really hate them. They'd rather do almost anything else. Entire aquarium product lines, schemes, and "husbandry philosophies" have been invented over the years to help limit- or even "eliminate"- having to do water exchanges.

Hobbyists go to great lengths and expense to avoid doing them, or to automate them. I've seen guys literally flood their homes- like, major "insurance-claim floods", by desigining and building complex automated water exchnaging systems for their tanks that failed. Expensive, complicated, semi-reliable stuff- all to avoid picking up a siphon hose.


In the mean time, I'll keep doing- and recommending- water exchanges. 

Oh, and speaking of water exchanges...both nitrate and phosphate are typically present in tap water...So when I espouse the use of an expensive RO/DI unit to "pre-treat" your tap water, I'm recommending a means to eliminate them at the source, giving you at least a good start. Reverse osmosis/deionization units, albeit somewhat pricy, are, in my opinion, an essential piece of equipment for any serious hobbyist. 

In general, the water quality of our botanical-influenced, natural systems is something worthy of a lot of research, experiments, and discussion in our community. There is so much interesting stuff happening in our tanks- and so many things we don't know...

However, for the things that we DO know, we're pretty focused on water quality, and long-term maintenance.

It's really a simple concept: Engaging in regular maintenance practices in botanical-style aquariums is really no different than in any other style of aquarium. The main distinction, as we've said like 5,000 times here, is to balance the practice of adding all of the botanical materials that we add with disciplined husbandry.

Nothing we can tell you is an absolute guarantee of perfect results...

It starts with preparation- a cornerstone of our botanical-style aquarium practice. Remember, you're dealing with natural materials, and the results you'll see are governed by natural processes that we can only impact to a certain extent by preparation before use.

And when it comes time to adding your botanicals to your aquarium, the second "tier" of this process is to add them to your aquarium slowly.

Like, don't add everything all at once, particularly to an established, stable aquarium. Think of botanicals as "bioload", which requires your bacterial/fungal/microcrustacean population to handle them.

Bacteria, in particular, are your first line of defense.

If you add a large quantity of any organic materials to an established system, you will simply overwhelm the existing beneficial bacterial population in the aquarium, which will likely result in a massive increase in ammonia, nitrite, and organic pollutants. At the very least, it will leave oxygen levels depleted, and fishes gasping at the surface as the bacteria population struggles to catch up to the large influx of materials.

This is not some sort of esoteric concept, right? I mean, we don't add 25 3-inch fishes at once to an established, stable 10-gallon aquarium and not expect some sort of negative consequence, right? So why would adding bunch of leaves, botanicals, wood, or other materials containing organics be any different?

It wouldn't.

So please, PLEASE add botanicals to your established aquarium gradually, while observing your fishes' reactions and testing the water parameters regularly during and after the process. Take measured steps.

There is no rush.

There shouldn't be.

It's interesting how the process of selecting, preparing and adding botanical materials to our aquariums has evolved over the time since we've been in business. Initially, it was all about trying to discover what materials weren't "toxic" in some way! Then, it was about figuring out ways to prepare them and make sure that they don't pollute the aquarium.

Finally, it's been about taking the time to add them in a responsible, measured matter, and to manage them as they break down in the aquarium.


I think our biggest "struggle" in working with botanicals is a mental one that we have imposed upon ourselves over generations of aquarium keeping:  The need to control our own natural desire to get stuff moving quickly; to hit that "done" thing...fast.

And the reality, as we've talked about hundreds of times here and elsewhere, is that there really is no "finished", and that the botanical-style aquarium is about evolution...

And it all starts with a certain "quality."

Stay diligent. Stay observant. Stay methodical. Stay patient...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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