The surest path to success with blackwater, botanical-style aquariums?

Periodically, it's neat to deviate from my "botanical philosophy" posts and some of our deep dives on more arcane aspects of blackwater. botanical-style aquariums, and focus on something more basic and practical.

Today, a little bit of a "refresher" once again.  Some of you who have been at this for a while don't need to hear it, but that many of our community would benefit from. I was thinking of a working title like, "How to crash your tank and kill your fishes with botanicals"; however, although a very descriptive title, leaving little doubt about what the topic is, I think it would be a bit too negative in tone. :)

But that's what today's little piece is about.

As our global "movement" expands, the excitement is palpable, and as more and more beautiful blackwater botanical-style tanks start showing up here and elsewhere online daily, it's easy to overlook the necessary practices and precautions required to manage an aquarium to get to the "ooh and ahh" phase! Much like what I've written about so many times, hobbyists seeing blackwater aquariums for the first time are often smitten with their "charms", and if they are, there is typically a desire to get going...quickly! And of course, the word "quickly" is always a scary one for us to hear. It's not as easy as purchasing a pack of botanicals from us and dumping them into your tank, and hey- "Instant Amazon!"


If you look back at the 500-some blogs we've published here on our site, that we regularly discuss process, patience, moving slowly, and the need to understand the way these tanks function, and how our practices can dictate the success- or failure- of a blackwater, botanical-style, aquarium. There is no special secret to keeping one of these aquariums successfully long term.  There is no dark cloud of doom waiting to take you down either- unless you don't make the effort to learn the function...The idea of maintaining a specialized aquarium of any type requires looking beyond those pretty pic of the finished product. Keeping a blackwater aquarium is no different from setting up and maintaining a planted aquarium, reef tank, African child tank, etc.- it starts with understanding the impacts of what we're doing when we add these materials to an aquarium, and how best to maintain them.

Once you get one of these systems established, and understand the "operating procedure" and some of the unique attributes of a lower pH system, there is absolutely no difference, "challenge wise" between a blackwater, botanical-style aquarium and any of the other aforementioned types of specialty systems. In fact, as someone who has maintained diverse, complex reef aquariums for almost three decades, as well as a 15,000 gallon coral propagation facility, I can tell you that a blackwater, botanical-style tank is way, way easier than almost any reef system I've kept. And I've probably killed more aquatic organisms in my career than most of you combined will ever kill- and a lot of it was as the result of sheer ignorance, bad judgement, or plain old arrogance. I share this not to wear as some "badge of honor", but to emphasize that I understand what can happen when you push too hard sometimes.

You just have to be slow, patient, and observant. 

Really, the easiest way to run into trouble when utilizing botanicals is to add a large quantity of these items to an existing aquarium in a relatively short span of time. What happens is that a large influx of organic material that can overwhelm the biological filtration capacity of the tank, while simultaneously depleting oxygen levels. A number of us know this firsthand from pushing it and ending up with fishes gasping at the surface- or worse. Remember, you're adding material which will decompose in the water, and if adequate nutrient export systems are not in place to deal with it, you could have some problems. This isn't some new revelation; it's something we've been talking about here for a long time. And it's common sense- "Aquarium-Keeping 101", really. We're just talking about adding lots of dried botanicals instead of lots of fishes or corals all at once, but it's the same kind of impact. However, it's important for us to bring up the potential "dark sides" in the context botanical-style aquariums now and again, as more and more hobbyists start experimenting with this stuff.

I've seen similar issues in reef tanks over the decades, when people overwhelm their systems with large influxes of live rock/fishes/corals. As we all know, aquariums are closed biological systems, and disrupting the "status quo" of their function (i.e.; changing inputs of material, etc.) requires observation, patience, monitoring, and adjustments to routine maintenance procedures. There is no mystery here. It's the same old story we've been taught for the better part of a century in fish keeping. 

So, how do you manage a "transition" of an existing system to a botanical-influenced blackwater aquarium safely?

The key is to:

A) Add botanical materials slowly, over the course of several weeks

B) Add modest quantities at any given time

C) Provide surface agitation to maximize gas exchange

D) Conduct regular water exchanges as you would with any aquarium.

E) Utilize some chemical filtration media, like Poly Filter, carbon, etc. during the initial additions or on a continuous basis as you see fit.

F) Monitor basic water chemistry (pH, alk, ammonia, nitrite) during the "transition, and ph/alk/nitrate (if you want) continuously as part of regular maintenance.

G) Employ good circulation within your system, which not only results in greater oxygenation and "mixing" of water "strata" - it physically suspends fine particulates in your system as well, making it easier for mechanical filtration to remove (of course, that assumes you don't like the look of "stuff" in the water, as some of us do!).

If there were ever a "hard and fast rule in the botanical/blackwater game, "Rule A" would be it. It's all about the cadence...the "secret", if you will, which sort of sets up everything else. And, by observing and assessing ("Rule F"), you'll get a real feel for how botanicals work in your aquarium.

Regular, though not obsessive- water parameter monitoring is always advisable to ascertain just what is going on in the aquarium. The need to monitor  parameters like ammonia, nitrite, and nitrate is obvious, but you also need to look at pH or TDS. When you're dealing with a lower ph, low carbonate hardness system, TDS may ultimately prove a more useful "yardstick" than pH in the long run, but for many of us, a good pH meter can provide an accurate assessment of the pH of the system regularly. We’ve talked previously about establishing “baseline” operating parameters for your tank, and trying to stay within that baseline for the life of the aquarium. And we've also talked about ammonia in a less toxic form at lower pH...Lots to refresh yourselves on here; we've covered some of this before, and no doubt we'll be discussing it again.

It's absolutely not doom and gloom, but the realities of any aquarium, as you know, are that, even with regular maintenance practices and monitoring in place, you can’t truly set a tank “on autopilot” and let it run itself. There is a constant “war” between good and bad chemical concentrations going on in your system, and you need to be on top of things in order to assure that the “bad” doesn’t outweigh the “good.”  

"Aquariums 101", right?

More or less.

On the more positive side, I've had some conversations with more science-minded botanical aquarists who postulate about the possibilities of fostering some form of denitrification in deeper botanical beds, and it is interesting! One of the questions that seems to come up a lot in this context is the extent to which hydrogen sulfide or other undesirable compounds can build up in a deep bed of compacted botanical materials.

In a botanical bed with materials placed on the substrate, or loosely mixed into the top layers, will it all "pack down" enough to the point where there is a complete lack of oxygen and we develop a significant amount of hydrogen sulfide or other nasty compounds in our tanks? I think that we're more likely to see some oxygen in this layer of materials, and I can't help but speculate that actual de-nitirifcation (nitrate reduction), which lowers nitrates while producing free nitrogen, might actually occur in a "deep botanical" bed.

And it's certainly possible to have denitrification without dangerous hydrogen sulfide levels. As long as even very small amounts of oxygen and nitrates can penetrate into the substrate this will not become an issue for most systems. I have yet to see a botanical-style aquarium where the material has become so "compacted" as to appear to have no circulation whatsoever within the botanical layer. Now, I base this on visual inspection of numerous tanks, and the basic chemical tests I've run on my systems under a variety of circumstances. I could still be wrong.

And another fun thing a number of you are thinking about and working on is the ability of a blackwater, botanical-style aquarium to function as a sort of "refugium", producing supplemental food sources for your fishes via fauna "resident" in the botanicals. Many of you can't help but wonder if our botanical tanks, simply by virtue of the fact that they have accumulations of decomposing plant materials, foster a significant enough of a population of "edible" microorganisms for fry to consume. In theory, I'd think so. However, the aquarist in me can't help but think that we should also consider stocking our aquariums with cultures of organisms like Paramecium and various "infusoria" at various times during the "startup" phase of our aquarium to sort of "kickstart" the populations, if reproduction of fishes is our goal. 

And there are so many more cool things to learn. But it starts with the basics that we all know, and applying some of that experience and knowledge to what, for many of you, is an entirely new style of aquarium.

The surest path to success with botanical-style, blackwater aquariums, as we've stressed repeatedly, is to move slowly and incrementally. Sure, one you gain experience, you'll know how far you can "push it", but, quite frankly- nature doesn't really care about your "experience"- if the conditions aren't right and the bacteria in your system cannot accommodate a rapid significant increase in bioload, she'll kick your ass like a personal trainer!

Respect nature. Learn from her.

Stay patient. Stay inquisitive. Stay humble. 

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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