Throwing some light on blackwater...

It goes without saying that the single most important component of our aquariums is also the most obvious...water! As the literal bearer of life and the environment in which our fishes, plants, and other organisms thrive, it's fundamental. it's the reason we're drawn to fishes, not gerbils, Tarantula, or Mice- or whatever other pets people keep!

Yeah, we're into water!

And I dear say that we take it for granted a bit.

Now, sure, some hobbyist rightfully place the importance of good quality, properly-conditioned water at the very top of their "want list" of "Stuff" required for successful aquariums. These are often fish breeders and very serious hobbyists, who understand the fundamental importance of good water for their work.

Some of the most common questions we receive lately are "How much _______ do I need to get my water to look like________?" or "How much_______ is needed to lower the pH in my tank?" Or, "How much do I need to get a good amount of humic substances and tannins into my aquarium?"

I usually respond with a simple, "I don't know."

These are all really good questions. Logical. Important.  I kind of feel like many hobbyists are looking for a plug-and-play "formula" or "recipe" for how to accomplish certain water-conditioning tasks.

I totally get that. But the reality is...there IS no "recipe" for how to do this stuff.

And it sucks, I know.

"Why, Scott? I read that you can just add some of this blackwater extract that you can buy online, and maybe add some catappa leaves, and..."

Stop. STOP. Please, we're just making this painful.

Simply adding leaves or bottled extracts to your tap water isn't going to result in "Instant Amazon" or whatever. There are numerous complexities and nuances which contribute to these habitats that to simply recommend adding "X" to your water isn't the whole story.

There are so many variables in the equation that it's almost impossible to give a definitive answer. And yeah, us guys in the botanical biz haven't really helped the situation. Over the years, vendors who sold catappa leaves, for example, would recommend starting amounts ("three leaves per 15 liters of water" or whatever...) of botanical materials to use in aquariums.

I mean, we've sort of done it, too...And, although our recommended "dosage" of leaves was given for different reasons (to avoid adding too much material to your tank too quickly), the idea of a "recipe" in general is kind of delusional, IMHO.

Now, this was all well and good, but it's based on....what? I mean, is this based on how many leaves of _______ size that a typical hobbyist with a 10-gallon aquarium needs to get the water "looking brown?" Or to lower tap water with a starting pH of 7.4 and a KH of ___ to pH of 6.9? Or to impart "x" ppm of tannins or humic substances into this given quantity of water?

See? Add to this story the fact that you really can't soften water and make it more "malleable" by using botanicals or extracts alone, and you've got a good case for confusion! It's just not that simple.

Maybe we can gain a bit of understanding- or at least, an appreciation for the dynamics of this process, by looking once again to Nature.

Have you very thought about how water reaches all of the wild aquatic systems of the world? I mean, it's got to get there some way, right? So, how does it reach the ponds, lakes, streams, and rivers and forest floors of the world?

Well, some simply falls into the body of water directly from the sky, and that's that. Some is a result of other overflowing streams and rivers (like, ya' know- those flooded Igapo forests we talk about!). Inputs of precipitation falling over the area of an aquatic habitat are transferred to the habitat via a number of different pathways.

It's surprisingly complicated.

There's like a whole field of science devoted to studying this process! It's called Hydrology, and it's incredibly interesting...As fish geeks, we're probably already acquainted with this field of study, at least tangentially! 

So, water comes from a variety of sources, reaching a myriad of ecological niches. However, not all of the water has such an easy journey on its way into our favorite aquatic habitat!

Even in the case of rainwater, some of it simply lands on tree leaves in the surrounding area and evaporates. This is a process scientists call "interception", and accounts for the fact that not all water makes it to the ground. Water that does reach the ground enters the soil through a process called infiltration. slowly percolating down to soil areas known as the "saturated zone"- and as you'd imagine, this is where the fun really begins! (to a soil geologist, at least!)

The soil properties control the infiltration capacity; these include things like soil permeability, the presence of vegetation and plant roots, and how much water is already in the soil. Through what is known as "ground water flow", ultimately, the water finds it way into our favorite aquatic habitats. It's important to note that soil texture ( the relative proportion of sand, silt and clay particles within the mix) affects infiltration rates. 

Sandy soils like the "podzols", common to forested areas of South America that we've talked about have higher permeability than some clay-based soils. In some really arid areas a "crust" can form on the soil surface, decreasing the permeability. And of course, the thickness of the soil directly affects how much water the soil can actually absorb.

And, in many cases, the substrate composition and its relationship with water has direct impact on the life forms which inhabit these aquatic systems. In the case of some habitats, like vernal pools, which are filled with water seasonally, the substrate is of critical importance to the aquatic life forms which reside there.

Yeah, soils and geology are perhaps the primary driver of water composition in Nature. 

Let's talk more about "blackwater."

In a blackwater environment, the color is a visual indicator of an influx of dissolved materials that contribute to the "richness" of the environment. Indeed, a blackwater environment is typically described as an aquatic system in which vegetation decays, creating  tannins that leach into the water, making a transparent, acidic water that is darkly stained, resembling tea.

But, that's not the whole story, really.

It’s important to really try to understand the most simple of questions- like, what exactly is “blackwater”, anyways?

A scientist or ecologist will tell you that blackwater is created by draining from older rocks and soils (in Amazonia, look up the “Guyana Shield”), which result in dissolved fulvic and humic substances, present small amounts of suspended sediment, and characterized by lower pH (4.0 to 6.0) and dissolved elements, yet higher SiOcontents. Magnesium, Sodium, Potassium, and Calcium concentrations are typically very low in blackwater. Electrical conductivity (ORP) is also lower than in so-called "whitewater" habitats.

Tannins are also imparted into the water by leaves and other botanical materials which accumulate in these habitats.


The action of water upon fallen leaves and other botanical-derived materials leaches various compounds out of them, creating the deep tint that many of us are so familiar with. Indeed, this "leaching" process is analogous to boiling leaves for tea. The leached compounds are both organic and inorganic, and include things like tannin, carbohydrates, organic acids, pectic compounds, minerals, growth hormones, alkaloids, and phenolic compounds.

Most of the of the extractable substances in the surface litter layer are humic acids, typically coming from decaying plant material. Scientists have concluded that greater input of plant litter leads to greater input of humic substances into ground water.

In other words, those leaves that accumulate on the substrate are putting out significant amounts of humic acids, as we've talked about previously! And although humic substances, like fulvic acid, are found in both blackwater and clear water habitats, the organic detritus (you know, from leaves and such) in blackwater contains more extractable fulvic acid than in clearwater  habitats, as one might suspect!

The Rio Negro, for example, contains mostly humic acids, indicating that suspended sediment selectively adsorbs humic acids from black water.  The low concentration of suspended sediments in rivers like the Rio Negro is one of the main reasons why high concentrations of humic acids are maintained. With little to no suspended sediment, there is no "adsorbent surface" (other than the substrate of the river, upon which these acids can be taken hold of (adsorb).

When you think about it, all of this this kind of contributes to why blackwater has the color that it does, too. Blackwater in the Amazon basin is colored reddish-brown. Why? Well, it has  those organic compounds dissolved in it, of course. And most light absorbtion is in the blue region of the spectrum, and the water is almost transparent to red light, which explains the red coloration of the water!

And many of those organic compounds come from the surrounding land, as touched on above...

In summary, natural "blackwaters" typically arise from highly leached (tropical) environments where most of the soluble elements in the surrounding rocks and soils are rapidly removed by heavy rainfall. Materials such as soils are the primary influence on the composition of blackwater.

Leaves and other materials contribute to the process and appearance in Nature, but are NOT the primary “drivers” of its creation and composition.


So, right from the start, it’s evident that natural blackwater is “all about the soils…” Yeah, I'll repeat it again: It’s more a product of geology than just about anything else. 

More confusing, recent studies have found that most of the acidity in black waters can be attributed to dissolved organic substances, and not to dissolved carbonic acid. In other words, organic acids from compounds found in soil and decomposing plant material, as opposed to inorganic sources. Blackwaters are almost always characterized by high percentages of organic acids.

Despite the appearance, as a general rule, blackwater rivers are lower in nutrients than clear rivers. Wouldn't it be interesting, when contemplating more natural biotope/biotype aquariums, to study and take into consideration the surrounding geology and physical characteristics of the habitat?  Too recreate the habitat based on the soil or geological composition of the surrounding terrestrial environment?

As we know now, the influence of factors like soil, and the presence of terrestrial materials like seed pods, leaves, and branches play a huge role in the chemical composition and appearance-of the water. It's really no different in the aquarium, right?

Like so many things in nature, the complexity of blackwater habitats is more than what meets the eye. Chemically, biologically, and ecologically, blackwater habitats are a weave of interdependencies- with soil, water, and surrounding forest all functioning together to influence the lives of the fishes which reside within them. No single factor could provide all of the necessary components for fish populations to thrive.

To damage or destroy any one of them could spell disaster for the fishes- and the ecosystem which supports them. It is therefore incumbent upon us to understand, protect, and cherish these precious habitats, for the benefit of future generations. 

And with regards to our aquarium work?

Although there may even be breakthroughs in terms of blackwater extracts and additives coming to market, there are still a lot of questions that would have to be answered before we could simply state that "X" drops per gallon of such an such a formula would yield a specific outcome. This reminds me of the reef aquarium world more an more, lol.

So, if I've made any "argument" here, it's that this stuff is every bit as much of an "art"- in terms of aquarium keeping- as it is a "science." We will, at least for the foreseeable future, have to use the data we have available and formulate a best guess as to how much of what can give us some of the impacts we are interested in for our aquariums.

We simply can't authoritatively make blanket statements like, "You need to use "X" catappa leaves per gallon in order to recreate Rio Negro-like conditions in your aquarium!" We can't simply state that you can throw in some podzolic soil and achieve blackwater, either. There are many factors in play, as we've discussed here, right?

Marketing hyperbole aside, we really are sort of...guessing.

And that's certainly nothing to be discouraged about!

We, as a community, are getting deeper into the functional aspects of blackwater, botanical-style aquariums than ever before. More light is being shed on what's going on in both our aquariums and in the natural habitats we desire to replicate. We are learning more every day about how the presence of tannins and humic substances in our aquariums is affecting the health, longevity, and spawning behaviors of our blackwater fishes.

We're learning about the challenges and realities of managing blackwater systems over the long term- understanding the good, the bad, and the dangerous possibilities that are present when we experiment with these ideas.

There is much, much more work to be done..And a lot of talented hobbyists like yourself are out there on the front lines every day, contributing to the body of knowledge that will benefit the hobby for generations!

Stay persistent. Stay bold. Stay open-minded. Stay curious. Stay disciplined...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


The hobby is easy, right?

Today. I'm sort of taking a contrary stance to what you might typically see in aquarium blogs. Okay, what else is new, right?

My position is this: The aquarium hobby, while not "difficult", is not super easy, either. And quite honest, it shouldn't be super easy. And we shouldn't be 'dumbing it down' so much.

Uh-ohh. Controversy time.

Well, before you go and label me a jackass and pelt me with "Hakkai Stones", think about it: We are creating and managing the entire environment for specialized living creatures. Unlike a dog or cat, which (at the risk of over simplifying things) just needs food and a place to sleep to survive, fishes require a place to live, the proper aquatic environment, including heat, nutrient export, food, oxygenation, and light. We also are responsible for creating a compatible community of animals, understanding the dynamics of the nitrogen cycle, quarantine, acclimation, disease identification and treatment, and a lot more.

Sure, having to master all of these that I things listed out makes it sound like we're freaking genius-level people to be successful. We don't have to be, of course (I mean, look at some of the clowns who are YouTube “influencers” and the drivel they generate...😂)- but we do have to understand and be able to execute successfully on a number of fronts in order not to kill our fishes immediately, don't we?

Now, a little bit of props to the fishes themselves! I mean, they're subjected to a lot of shit before they get to us, right? Wild fishes, especially, undergo a real trial just to get to us: Collection, sorting by the fishers, a few days at a exporter's facility, a flight from their home country, a stint at a wholesaler, then on to the LFS, and finally to you. All the while, adapting to varying conditions, crowding, and little, if any food. When you think about it, it's hard to believe that they survive at all!


Back to our gig.

As hobbyists, we're morally obligated to have at least a rudimentary understanding of the requirements which our fishes need to survive and thrive. And, unfortunately, in today's "Insta-fast"  "Everyone can go from zero to hero in three days" social-media-driven hobby, many hobbyists simply don't have that. In fact, if you asked 10 hobbyists some of the most basic aquarium-related questions, such as how the nitrogen cycle works, or what pH means, I'll wager that you'd likely get 3-4 hobbyists who couldn't articulate anything about these topics.

However, if you ask them about the best aquascaping rock, trendy approach, or stupidly-named wood type, I'll bet they'll be able to tell you everything you'd care to know.

That's indicative of a problem. When we accept this level of mediocrity, we're making ignorance of the art and science of aquarium keeping cool.

That's crazy.

We're better than this.

We as hobbyists need to educate ourselves before we leap. Now, at this point, there are likely a few readers/listeners who will be like, "Damn, Captain Buzzkill, you're making it like you have to be a freaking marine biologist to be able to keep tropical fish! WTF?"

My response?

No, I'm not. And pointing out reality doesn't make me a complete asshole. Well, sort of an asshole- but not a complete one! 😆

Seriously, though, there is something really wrong when we have hobbyists trying all sorts of crazy expensive and exotic hobby ideas and equipment, when their fundamental understanding of the aquarium hobby is essentially inadequate.

Like, we've created a generation of hobbyists who want to run before they can walk. They're always looking for "hacks" and shortcuts for "making things easier." And when they fail- they have no way to understand why. And they often quit the hobby as a result. I've seen this dozens of times during my hobby "career." And we- the industry, creators, and communicators of the aquariums hobby- are responsible for this.

Now look, I'm all for making things easier, but NOT for dumbing down stuff. It shouldn't be like having to take board examinations in order to keep a fish tank, and setting up and caring for a tank shouldn't always be onerous- but you should at least try to have a working knowledge of a bunch of fundamental topics before you plunk down your cash and put fishes' lives on the line, right? And you should want to. And we as hobbyists should be interested in learning and acquiring the basic skills necessary to assure a good start in the hobby. We don't need to make this a task; we just need to do a little basic research first. 

This is where the local fish store can excel.

The "mentoring" you can receive from a quality fish store is one of the best first exposures you can have to the art and science of aquairum keeping. As long as they don't take a purely sales-oriented approach to things (and most don't, despite the popular, persistent hobby mythology of the buffoonish, ignorant, and predatory LFS personnel that have been the stuff of online lore for decades now). Most LFS staff are uber hobbyists, obsessed with aquariums and fishes, and have a vested interest in seeing their customers succeed.

For those who need to get their "education" online, there are a lot of good resources. I don't need to rehash that. However, despite its popularity and search ability, YouTube isn't always the best source. There ARE a lot of great channels out there, but there is also a disproportionately high number of outright garbage, too. Channels in which the "creator" seems to have absolutely no clue about the topic he/she is authoritatively spewing. In our own sector alone, I've seen this several times. It's vomit inducing. 

And a lot of the stuff out there- even "sponsored content"- is about drivel...doing a certain scape with this cool rock, or how to arrange wood so that your tank looks like everyone else's', or something equally as vapid. There is proportionately little produced about fundamental hobby stuff.

We can't run from some of the science stuff...I mean, we are ALL at the mercy of the nitrogen cycle, for example, and we need to have at least a basic understanding of how it works and what the implications are for our aquarium work. It's actually really important!

When I co-owned a coral propagation/import business, a scarily high percentage of the questions from customers were frighteningly basic- like stuff you should know before you ever even buy any aquarium, let alone set up a reef tank.


Back in those days, I literally received calls from hobbyists who didn't have the most rudimentary understanding of the needs of corals, let alone, the nitrogen cycle- yet they spent tens of thousands of dollars outfitting their reef tank with the latest gear, and buying the latest "designer frags."

it was head-scratching, to say the least. It was downright discouraging on some days.

It's not just limited to the reef world, of course. It’s all over the hobby. 

And, it's our fault as an industry, too.

We seem to sell prepackaged "solutions" for everything. Another piece of gear, another additive..."That'll solve your problems!" We seem to be happier just selling people a product that we hope will solve their problems. Laughably, I've seen soem vendors/manufacturers trot out the pathetic line about their product making things easier so you could "enjoy the hobby more!" Like, WTF? Isn't feeding your fishes, doing water exchanges, and just managing the tank part of what makes it enjoyable, too? Or is the only enjoyable part of the hobby humble-bragging on The 'Gram about our latest aquascape?

How about we educate people on the basics and beyond? The good, the bad, and the shitty? That will make the use of your product a lot more logical. Yet, I know- it takes time. It's more difficult to educate people on the underlying problem...the reason why people would need your product in the first place. It's much easier to just tell them what to buy and that's that. It sells stuff faster. But it doesn't build a long-term hobbyist. That's why we at Tannin have article after article on the most basic, and even arcane aspects of playing with blackwater/botanical-style aquariums on our site.

Because I believe that hobbyists have to be armed with the most fundamental knowledge of our craft in order to succeed. I'm not going to just show pretty pics of cool 'scapes and sell seed pods and leaves that way. That's how I'm going to do my part to address the hobby dropout thing. My friends James of Blackwater UK and Ben of Betta Botanicals, two vendors as geeked out as I am about this stuff, are on the same page as me. We're determined to show hobbyists that the process- the whole thing- is as much fun as just looking at the number of likes your tank pics get on your fave social media channel.

It's a wider hobby "cultural problem", too. We're lazy. A lot of us want instant gratification and simply don't want to take the time to dig through information- even if it's out there in abundance. They want it easier. Faster. More concise.

And yes-I know. Everyone is "busy", etc. Yet, why have a hobby in the first place if you don't want to spend time playing with it and educating yourself about it? People can't be lazy. They have to learn the underlying, fundamental stuff. They need to read, watch, discuss, observe. A personal example again? I get numerous emails asking me how to prepare botanicals- even after we spent hundreds and hundreds of dollars on producing a customized infographic card that goes in every order, and years writing dozens of articles on this very topic.

Some people seem so unwilling to do the most basic research! What a shame.  I mean, Google is one of the greatest inventions in the history of humanity, making information about virtually any topic imaginable available anywhere, any time, to anyone. Easily.

Yet, many figure the "hack" is just to ask someone and expect them to give concise answers on how to do everything, instead of taking the extra time to educate themselves a bit before just mailing it in and prodding someone else for the answer. Yeah, we've somehow decided that a DM to someone for a “quick answer” is a better way to acquire knowledge than typing in the keywords, like "what is the nitrogen cycle?" and learning it once and for all. 

Obviously, as an industry guy and writer- I'm always going to help those with questions when I can...But I also need to encourage self-research, too. I still need to do better at disseminating information. We all do.

There's blame enough to go around. And to newbies and others in the hobby-my plea to you:

Don't be freaking lazy. The resources are there.

We just have to keep directing people towards them. And people need to use them. And we have to emphasize the fundamentals of the hobby. Not just the cool creative stuff. Sure, not everyone is great at conveying technical concepts to people in an easy-to-understand manner. However, we can try, Because, when no one is doing that, we end up with 14,000 channels on how to "scape a blackwater aquairum" and not a single one explaining what the hell blackwater is, and how to manage the ecology of a blackwater system.

That's a problem, IMHO.

Everyone wants to do the "fun" stuff, hype their sponsors' products, and get all of that recognition. Yet, without discussing the less sexy fundamentals, the "fun stuff" just becomes a waste of precious animal lives and lots of money. People get frustrated and quit the hobby. When I see the words "paid partnership" under an Instagram post lately, I almost reflexively (and often correctly, I'm afraid) assume that it's usually drivel. Because most of the creators- and the brands who sponsor them- have accepted a level of superficiality as the norm. And that's really sad. These people are too talented to waste their followers' precious attention- and their sponsor's money- by producing such mindless fluff.

The "creative" and "trendy" is valued over the substance, even by brands. And the irony is that doing a little more substance in a creative manner is what will sell more product and build a stronger brand in the long run. Yet, it's easier to just pay some "creator" do a fun little video with a bit of hip-hop music, the appropriate sponsor hashtags, and consider it a job well done.

I call bullshit on that.

Brands need to stop paying these "creators" for this garbage.

You can still be creative and edgy and cool while conveying complex or arcane topics... Hell, we do it all the time here (so modest, right?).

Yes, even in the social media "Insta-hype" world we're in, there is room for improvement. I've hit this hard before...we all show too much "finished product" with killer aquascapes and such, and not enough of the less sexy, although way more important process...

There is an easy fix for that one. Just share the process. 

Discuss the fundamentals of what you do.

When hobbyists realize it's not just "1-2-3 AWESOME!"- and that there is a little work, and occasional setbacks and struggle involved, expectations are set which assure people go in with their eyes wide open...and stay in. Expectation management via education. And there is a certain responsibility that we as hobbyists take on when keeping live fishes; this needs to be emphasized.  And guess what, fellow aquarium brands? They'll still buy your product. In fact, they'll probably be more likely to, because they will have a fundamental understanding for why they need it.

No. The aquarium hobby isn't that easy.

But it's not ridiculously hard, either. 

We have a responsibility as hobbyists to keep these precious creatures alive and happy. And we as hobby and industry people have an obligation to tell it like it is. To touch on fundamentals. To explain things. To convey that, while not overly complex, some the underlying information that you need to know to be successful in the hobby is vital. Even if it requires a bit of reading and discussion in order to grasp it. And that it's every bit as interesting as selecting the right stones for your next fantasy 'scape.

In our world, there is a reason why we talk so much about ecology and arcane things, like the idea of allochthonous input into wild aquatic habitats. There is a reason why we devote hundreds of thousands of words to subjects like fungi, biofilms, and detritus. It's because an understanding of these topics is foundational to the work we do as botanical-style aquarium enthusiasts. When you understand these things, you're better equipped to understand what's happening in your aquairums. 

It would have been much easier for me if I spent the last 6 years writing articles and doing podcasts on how to get the sexy look of a botanical-style aquarium. Yet, it would have left us simply another hollow, vapid purveyor of leaves and seed pods, passing the buck to someone else to cover these ideas, develop the operating fundamentals and philosophies which are applicable to the botanical-style aquarium methodology.

Not on my watch.

I'm going to continue discussing some of these seemingly arcane topics. Why? Well, for several reasons. First, because someone has to do it. Might as well be me; I play with this stuff every day of my life. Second, because it's so important to convey these fundamentals. It builds a movement and reinforces the methodology we all embrace. Third, because I feel that I have a responsibility to the hobby, and to the fishes we love. And finally, because it's hard. It's not easy to distill these complex ideas into digestible information. And that very fact makes it a worthwhile endeavour.

We all need to learn, understand, and share these types of topics.

Success in the aquarium hobby isn't that difficult- after you have a grasp of the fundamentals; an understanding of why we do what we do. However, the hobby isn't "easy" in the sense that you just toss your fishes into the water and call it a day. It takes some work. It should take some work. Because taking care of live animals, some of which are threatened in the wild, is a huge responsibility which should not be taken lightly.

So, maybe the tone of this piece is a little bit dark to some. It shouldn't be interpreted that way. Rather, it's a brutally honest call for us to make a better effort to understand and appreciate just how amazing what we as aquarists do every dingle day, and what responsibility goes along with these achievements. It's a call to wake up- look ourselves in the mirror as hobbyists, content creators,  and industry types- and do better.

We can. There is enormous talent out there- and there has never been a time in history when its easier to disseminate useful information to a larger number of interested persons. 

We just have to DO it. To not shirk this responsibility- and this gift.

It's not as hard as you think, and the benefits of the effort are remarkable.

Stay honest. Stay reflective. Stay creative. Stay observant. Stay inspired...

And Stay Wet.


Scott Fellman

Tannin Aquatics 



Accumulating botanical materials...and mental toughness!

They say that Nature abhors a vacuum...

Nature also seems to like to accumulate stuff, doesn't it? 

Natural watercourses are really good at accumulating terrestrial materials, creating inviting habitats for fishes. They serve not only as physical locales for fishes to forage an hide amongst, they provide a huge habitat for a variety of other organisms which support the fishes.

And of course, these are compelling aquatic features for us fish geeks to replicate in our aquariums, aren't they? They are, and perhaps provide the basic "role model" for the botanical-style aquairum.

These aggregations of materials occur all the time in Nature, and they're caused by a variety of things; typically, weather events, which drive materials off of the trees overhead, or from the surrounding terrestrial habitats into the water. Currents caused by rising water levels move the materials along, until they might be caught up among various benthic features, like fallen trees, branches, rocks, etc.

Yeah, as you'd imagine, stream and river bottom composition is completely affected by things like weather, current, geology, the surrounding terrestrial habitat, and a host of other factors- all of which could make planning your next aquarium even more interesting if you take them into consideration! 

According to one study I read, eventually, most of the organic debris is deposited on the stream bottom or drifts downstream until it becomes trapped by a variety of natural obstacles.

If we focus on streams, it's important to note that the volume of water entering the stream, and the depth of the channels it carves out, helps in part determine the amount and size of materials which accumulate, as well as the sediment particles that can be carried along, and thus comprise the substrate of this habitat. .

And of course, the composition of bottom materials and the depth of the channel are always changing in response to the flow in a given stream, affecting the composition and ecology in many ways.

Some leaf litter beds form in what stream ecologists call "meanders", which are stream structures that form when moving water in a stream erodes the outer banks and widens its "valley", and the inner part of the river has less energy and deposits silt- or in our instance, leaves.

There is a whole, fascinating science to river and stream structure, and with so many implications for understanding how these structures and mechanisms affect fish population, occurrence, behavior, and ecology, it's well worth studying for aquarium interpretation!  Did you get that part where I mentioned that the lower-energy parts of the water courses tend to accumulate leaves and sediments and stuff?

Likely you did!

Permanent streams will often have different volume and material composition (usually finely-packed sands and gravels, with lots of smooth stones) than more intermittent streams, which are the result of inundation caused by rain, etc.

So-called "ephemeral" streams, typically occur only immediately after rain events (which means they usually don't have fish in them unless they are washed into them from more permanent watercourses). The latter two stream types are typically more affected by leaves, botanical debris, branches, and other materials.

In the Amazon region (you knew I was sort of headed back that way, right?), it sort of works both ways, with the rivers influencing the surrounding land...and then the land "giving" some of the materials back to the rivers...the extensive lowland areas bordering the river and its tributaries, known as varzeas (“floodplains”), are subject to annual flooding, which helps foster enrichment of the aquatic environment.

Land and water, working together, provide and amazing resource for the adventurous and interested hobbyist to explore in greater detail.

The important, and overriding Thieme of many aquatic habitats which we try to replicate in the hobby is that they accumulate quantities of terrestrial materials. These materials don't just impact the physical characteristics of these habitats, they influence the ecology as well. As we know by now, terrestrial materials, when submerged in water, leach soluble compounds into the water, impacting the chemistry.

They also tend to recruit fungal growths and biofilms, which in turn serve to not only decompose the terrestrial materials- they tend to attract fishes to graze upon them! Terrestrial materials form the basis of a rich, surprisingly complex aquatic ecology. A food web arises.

So, what exactly is a food web?


A food web is defined by aquatic ecologists as a series of "trophic connections" (ie; feeding and nutritional resources in a given habitat) among various species in an aquatic community. 

All food chains and webs have at least two or three of these trophic levels. Generally, there are a maximum of four trophic levels. Many consumers feed at more than one trophic level.

So, a trophic level in our case would go something like this: Leaf litter, bacteria/fungal growth, crustaceans...

In the wild aquatic habitats we love so much, food webs are vital to the organisms which live in them. They are an absolute model for ecological interdependencies and processes which encompass the relationship between the terrestrial and aquatic environments.

Interestingly, in streams, the primary producers of the food webs that attract our fishes are...algae and diatoms, which are typically found on rocks and wood wherever light and nutrients create optimum conditions for their growth. Organic material that enters streams via leaf fall is acted upon by small organisms, which help break it down.

It is probably no surprise, then, that bacteria (especially in biofilms!) and fungi are the initial consumers of the organic materials that accumulate on the bottom. Like, the stuff many of us loathe. These, in turn, are extremely vital to fishes as a food source. Hence, one of the things I love so much about utilizing a leaf litter bed as a big part of your substrate composition in an aquarium!

We are able to establish rudimentary food webs in our aquariums. It's pretty easy, if we don't try to clean the crap out of our tanks and remove every bit of organic matter which we deem offensive to our aesthetic sensibilities! Remember, all of that material which we freak out about is someone's next meal, isn't it? It's consumed. The various organisms which arise when we allow leaves, branches, seed pods and other materials to accumulate and decompose in our tanks help see to that.

Yes, aquariums are different than wild aquatic habitats, but they have many characteristics which are analogous to them. And, sure, we typically don't maintain completely "open" systems, but I wonder just how much of the ecology of these fascinating habitats we can replicate in our tanks-and what potential benefits may be realized?

I'm willing to bet that it's a lot more than we think. However, we have to start somewhere, right?

It all starts with adding and accumulating terrestrial materials in our tanks, and allowing an ecology to grow up around them. It's that simple- and that complex, right? It falls on us- the hobbyists- NOT to go crazy and try to intervene too much. We need to exercise restraint- to let the natural processes which power our aquariums arise, assemble, and thrive.

Hands off! 

That's my continuing challenge to our community..

Yeah, we have to let stuff go a bit. It's really hard for a lot of hobbyists to do this. We're essentially trained from the beginnings of our aquarium experience to scrub, polish, and siphon out everything which doesn't meet some definition of "acceptable."

We've been told that algae growth or fungal growths on our wood or substrate are bad, and must be removed. We've been encouraged to siphon out any decomposing materials, and that stuff like detritus is the source of untold disaster if we let it accumulate in our tanks.

It's hard to make this mental shift. I know. I've been trying to convince people to take this path for the better part of the past decade, and it's finally catching on. Skeptics and haters abound- more than ever, now, as these ideas have gained traction in the aquarium hobby.

It's 100% counterintuitive to everything we've been indoctrinated to believe. And worse, we're asking you to have faith that "stuff will work out" in your tank when you see all of this biofilm and fungal growth, turbid water, decomposition, and perhaps even algae. Stuff that the so-called "Nature Aquairum" crowd would absolutely shit their pants over. 

Well, this IS Nature, boys and girls. 

This is Planet Earth.

And yeah, you're actually not 100% in control. It's not the sanitized, organized, highly stylized "Nature" of your fantasies. It's the "Nature" that's perfectly imperfect, filled with non-ratioed, seemingly disorganized aggregations of materials, and life forms covering everything. You have to cede some of the work in your tank to Nature. You'll "go through some things." Some of the stuff you'll see will be "ugly" to you.

Or, will it be?

Will you perhaps study some of the wild aquatic habitats of the world where our fishes come from, see what makes them function the way that they do- and draw a parallel between what you're seeing in your tank, and what you're seeing in Nature?


Will you hang on?

Will you "wait out" what appears to be an endless explosion of gooey stringy stuff coming out of your leaves, wood, and  and botanicals, and allow your tank to achieve it's own form of equilibrium? Or, will you reach for the siphon hose and pull it all out, disrupting some of Natures's most elegant, valuable, and efficient processes in order to "re-set" and achieve some sort of "instant gratification" that you were told that a spotless, sterile-looking tank will provide?

Yeah. Re-setting the whole thing.

Doing things the way we've done them in then hobby for decades because they give you the predictable results in a short amount of time...

Or, will you see the real beauty of unedited Nature in your very own tank? And the amazing way Nature works it out...If you let Her.


That's the adventure- the challenge of the botanical-style aquarium. A methodology filled with inexact, unconventional, yet well-known natural processes. A methodology which asks you to make some leaps of faith, some educated guesses, and to play some hunches. An evolving, not entirely predictable path to a dynamic, truly remarkable aquarium.

You can do this. You might fail, but you'll likely succeed, especially if you put your faith in Nature.

Be strong. Be patient. Be experimental.

Hang on through the weird, uncomfortable, uncertain, unknown stuff. It's worth it. 

Stay bold. Stay open minded. Stay curious. Stay the course...

And Stay Wet.


Scott Fellman

Tannin Aquatics 








Epiphytes, macrophytes, allochthonous input, and other "natural" fish foods...

As a hardcore enthusiast of the blackwater/botanical-style aquarium, you're more than well-attuned to the nuances involved in managing a system filled with decomposing leaves, seed pods, wood, etc. And you're keenly aware of many of the physiological/ecological  benefits that have been attributed to the use of these materials in the aquarium. However, I am willing to bet that most of us have not really considered the "nutritional" aspects of both botanicals and the life forms they foster as an important part of the "functional/aesthetic" dynamic we've touched on before.

Let's consider some of the types of food sources that our fishes might utilize in the wild habitats that we try so hard to replicate in our aquariums, and perhaps develop a greater appreciation for them when they appear in our tanks. Perhaps we will even attempt to foster and utilize them to our fishes' benefits in unique ways? 


One of the important food resources in natural aquatic systems are what are known as macrophytes- aquatic plants which grow in and around the water, emerged, submerged, floating, etc. Not only do macrophytes contribute to the physical structure and spatial organization of the water bodies they inhabit, they are primary contributors to the overall biological stability of the habitat, conditioning the physical parameters of the water. Of course, anyone who keeps a planted aquarium could attest to that, right? 

One of the interesting things about macrophytes is that, although there are a lot of fishes which feed directly upon them, the plants themselves are perhaps most valuable as a microhabitat for algae, zooplankton, and other organisms which fishes feed on. Small aquatic crustaceans seek out the shelter of plants for both the food resources they provide (i.e.; zooplankton, diatoms) and for protection from predators (yeah, the fishes!).

So, plants in the aquarium have been valued by aquarists "since the beginning" for all sorts of benefits- that's not really groundbreaking. I personally think that one of the more interesting functions of plants in the aquarium is to serve as this sort of "feeding ground" for fishes in all stages of their existence. Oh, yeah, they look cool, too! 

Perhaps most interesting to us blackwater/botanical-style aquarium people are epiphytes. These are organisms which grow on the surface of plants or other substrates and derive their nutrients from the surrounding environment. They are important in the nutrient cycling and uptake in both nature and the aquarium, adding to the biodiversity, and serving as an important food source for many species of fishes.

In the case of our aquatic habitats, like streams, ponds, and inundated forests, epiphytes are abundant, and many fishes will spend large amounts of time foraging the biocover on tree trunks, branches, leaves, and other botanical materials. Although most animals use leaves and tree branches for shelter and not directly as a food item, grazing on this epiphytic growth is very important. Some organisms, such as nematodes and chironomids ("Bloodworms!") will dig into the leaf structures and feed on the tissues themselves, as well as the fungi and bacteria found in and among them. These organisms, in turn, become part of the diet for many fishes.

And the resulting detritus produced by the "processed" and decomposing pant matter is considered by many aquatic ecologists to be an extremely significant food source for many fishes, especially in areas such as Amazonia and Southeast Asia, where the detritus is considered an essential factor in the food webs of these habitats. And of course, if you observe the behavior of many of your fishes in the aquarium, such as characins, cyprinids, Loricarids, and others, you'll see that in between feedings, they'll spend an awful lot of time picking at "stuff" on the bottom of the tank. In a botanical style aquarium, this is a pretty common occurrence, and I believe an important benefit of this type of system. 

I am of the opinion that a botanical-style aquarium, complete with its decomposing leaves and seed pods, can serve as a sort of "buffet" for many fishes- even those who's primary food sources are known to be things like insects and worms and such. Detritus and the organisms within it can provide an excellent supplemental food source for our fishes! It's well known that in many habitats, like inundated forests, etc., fishes will adjust their feeding strategies to utilize the available food sources at different times of the year, such as the "dry season", etc. And it's also known that many fish fry feed actively on bacteria and fungi in these I suggest one again that a blackwater/botanical-style aquarium could be an excellent sort of "nursery" for many fish species! 

You'll often hear the term "periphyton" mentioned in a similar context, and I think that, for our purposes, we can essentially consider it in the same manner as we do "epiphytic matter." Periphyton is essentially a "catch all" term for a mixture of cyanobacteria, algae, various microbes, and of course- detritus, which is found attached or in extremely close proximity to various submerged surfaces. Again, fishes will graze on this stuff constantly.

And then, of course, there's the "allochthonous input" that we've talked about so much here: Foods from the surrounding environment, such as flowers, fruits, terrestrial insects, etc. These are extremely important foods for many fish species that live in these habitats. We mimic this process when we feed our fishes prepared foods, as stuff literally "rains from the sky!" Now, I think that what we feed to our fishes directly in this fashion is equally as important as how it's fed.

I'd like to see much more experimentation with foods like ants, fruit flies, and other winged insects. Of course, I can hear the protests already: "Not in MY house, Fellman!" I get it. I mean, who wants a plague of winged insects getting loose in their suburban home because of some aquarium feeding experiment gone awry, right?

That being said, I would encourage some experimentation with ants and the already fairly common wingless fruit flies. Can you imagine one day recommending an "Ant Farm" as a piece of essential aquarium food culturing equipment? Why not right?

As many of you may recall, I've often been amused by the concerns many hobbyists express when a new piece of driftwood is submerged in the aquarium, often resulting in an accumulation of fungi, algal growth and biofilm. I realize this stuff looks pretty shitty to most of us, particularly when we are trying to set up a super-cool aquascaped tank. That being said, I think we need to let ourselves embrace this. I think that those of us who maintain blackwater. botanical-style aquariums have made the "mental shift" to understand, accept, and even appreciate the appearance of this stuff.

When you start seeing your fishes "graze" casually on the materials that pop up on your driftwood and botanicals, you start realizing that, although it might not look like the aesthetics we had in mind, it is a beautiful thing to our fishes. And this made me think that an "evolved" preparation technique for driftwood might be to "age" it in a large aquarium that also serves as an acclimation system for certain fishes. For example, fishes like Headstanders (Chilodus punctatus) and various loaches, catfishes, and others, would be excellent additions to this "driftwood prep tank." You could get the benefit of having the gunky stuff accumulate on the wood outside of your main display (if it bothers you, of course), while helping acclimate some cool fishes to captivity!

Just throwing the idea out there.

And of course, we've talked before about the "botanical nursery" concept- creating an aquarium for fish fry that has a large quantity of decomposing botanicals and leaves to foster the production of these materials, which serve as supplemental food for your fish fry. I have done this before myself and can attest to its viability. You fishes will have a constant supply of "natural" foods to supplement what you are feeding them in the early phases of their life. Learn to make peace with your detritus! 

This little discussion has probably not created any earth-shattering "new" developments, but I believe that it has at least looked at a few of the terms you see bandied about now and again in hobby literature, perhaps clarifying their significance to us. And I think it's really about us understanding what happens in nature and how we can work with it instead of against it, taking advantage of the food sources that she provides to our fishes when we don't rush off for the algae scraper and siphon hose before considering the upside!

Another "mental shift", I which many of you have already made, no doubt. I certainly look forward to seeing many examples of us utilizing "what we've got" to the advantage of our fishes! 

Stay bold. Stay open-mined. Stay interested. Stay creative. Stay engaged.

And Stay Wet.


Scott Fellman

Tannin Aquatics