Compelling questions...detailed answers...More from "the mail bag..."

As you know, we receive a fair number of questions from you, our community, about any number of topics relating to botanical-style aquariums and the habitats which they represent.

Today, let's answer a couple we've received recently about leaf litter beds and mindset behind the use of botanicals in our aquariums.

Of course, these questions got me "riffing" about the concepts, techniques, and executions that we bring to the table when we play with this stuff. Both questions got my "writing juices" going and were literally worthy of their own blogs! Keep 'em coming! 

Here goes:

Q- Scott, I understand that you're interested in leaf litter beds in aquariums. I'm thinking of constructing a litter bed in my 40 gallon blackwater aquarium. Could you give me a quick explanation of the benefit for my fishes of doing this? Thanks!

JP, Prescott, Arizona USA

Well, a "quick" explanation from me is always a challenge- but here goes, JP!

I'm obsessed with leaf litter in the wild and in the aquarium. I think it's because it's literally an oasis of life. Compelling, diverse, and productive. So, we need to think about them a bit in the context of the wild habitats, first.

Many tropical rivers and streams are characterized by large quantities of leaf litter and decaying botanicals on the bottom, with typically clear (but tinted) water. As discussed many times in this column, leaf litter is used as shelter, spawning ground, feeding area, and in some instances, as supplemental food itself. This is a highly productive habitat in nature that also just happens to look really cool in our aquariums, performing exactly the same function!

Fish population density is often correlated with the availability of food resources- and, as we've discussed many times here, leaf litter beds are highly productive food resources! In wild habitats, there have been many instances where researchers have counted literally hundreds of fishes per square foot inhabiting the matrix of botanical materials on the bottom of stream beds, which consists primarily of leaf litter.  As dead leaves are broken down by bacterial and fungal action, they develop biofilms and associated populations of microorganisms ("infusoria", etc.) that are an ideal food source for larval fishes.

When you take into account that blackwater environments typically have relatively small populations of planktonic organisms that fish can consume, it makes sense that the productive leaf litter zones are so attractive to fishes!  That being said, leaf litter beds are most amicable to a diversity of life forms These life forms, both planktonic and insect, tend to feed off of the leaf litter itself, as well as fungi and bacteria present in them as they decompose.

It all starts with those leaves...

The leaf litter bed is a surprisingly dynamic, and one might even say "rich" little benthic biotope, contained within the otherwise "impoverished" waters. And, as we've discussed before on these pages, it should come as no surprise that a large and surprisingly diverse assemblage of fishes make their homes within and closely adjacent to, these litter beds. These are little "food oasis" in areas otherwise relatively devoid of food.

The fishes are not there just to look at the pretty leaves, trust me...

Major blackwater rivers like the Rio Negro and Orinoco are often called "impoverished" by scientists, in terms of plankton production. They show little seasonal fluctuations in algal and bacterial populations.  This is a fact borne out by many years of study by science. However, "impoverished" doesn't mean "devoid" of life. And in many cases, these populations of food organisms do vary from time to time- and the fish along with them.

Other blackwater systems do show seasonal fluctuations, such as lakes and watercourses enriched with overflow in spring months. At low water levels, the nutrients and population of these life forms are generally more dense.

Creatures like hydracarines (mites), insects, like chironomids (hello, blood worms!), and copepods, like Daphnia, are the dominant fauna that fishes tend to feed on in these waters. When you study gut-content analysis done by ichthyologists on fishes found in these habitats, this is predominantly what you find. This is interesting to contemplate when we consider what to feed our fishes in aquariums, isn't it? 

There's a lot of food out there, for the fishes willing to look for it...which, pretty much all of them devote most of their lives to doing, lol

It's not really that much different in the aquarium, is it? I mean, as the leaves and botanicals break down, they are acted upon by fungi and bacteria, the degree of which is dependent upon the available food sources. Granted, with fishes in a closer proximity and higher density than in many wild systems, the natural food sources are not sufficient to be the primary source of food for our fishes- but they are one hell of a supplement, right?

That's why, in a botanical-rich, leaf litter dominated aquarium, you see the fishes spending a lot of time foraging in and among the litter...just like in Nature. 


Q-Hey, Scott! LOVE your blogs and podcasts! I have also long been a fan of Amano's Nature Aquarium books, although I think that his old works are not like the ones we see everyone playing with. I've heard you mention that you are a fan of his, too, and feel like the botanical aquarium draws somewhat from his early works, and I'm inclined to agree with you. Can you explain this further?

RK, Wilmington, DE, USA

Ohhh- a LOT to unpack here...I could go on and on about this...Stop me...

When you consider the types of aquariums that we work with, I would imagine that it IS probably funny to outsiders, or those new to our little obsession, to hear us going on and on about utilizing dried leaves, twigs, and seed pods in our aquariums with words such as "methodology" and "technique" and the like.

I can't help but think that Amano, who spent years studying many aspects of Nature and her influence on the aquatic environments, would really love this stuff!!  I think that he'd love the unique aesthetics, sure- but I think he'd especially love how these ephemeral materials we play with can influence the way our aquariums function.

It's the essence of his embrace of the Japanese philosophy of wabi-sabi. I think he'd gently scold the hobby and perhaps lament how it has embraced mostly the more superficial aspects of Nature, beautiful as they are- as opposed to "the whole picture" in aquarium work- sanitizing and editing it along the way, versus representing Nature as it is...

I suppose that there are occasional smirks and giggles from some corners of the hobby when they initially see our tanks, with some thinking, "Really? They toss in a few leaves and they think that the resulting sloppiness is "natural", or some evolved aquascaping technique or something?"

Funny thing is that, in reality, it IS a sort of evolution, isn't it?

I mean, sure, on the surface, this doesn't seem like much: "Toss botanical materials in aquariums. See what happens." It's not like no one ever did this before. And to make it seem more complicated than it is- to develop or quantify "technique" for it (a true act of human nature, I suppose) is probably a bit humorous. 

Yeah, I can see that...

On the other hand, the idea behind this practice is not just to create a cool-looking tank...

And it's not about making excuses for abandoning aquarium "best practices" as some justification for allowing our tanks to look like they do.

We don't embrace the aesthetic of dark water,  a bottom covered in decomposing leaves, and the appearance of biofilms and algae on driftwood because it allows us to be more "relaxed" in the care of our tanks, or because we think we're so much smarter than the underwater-diorama-loving, hype-mongering competition aquascaping crowd.

Well, maybe we are? 😆 (I promise to keep dissing these people until they put their vast skills to better use in the hobby...)

I mean, we are doing this for a reason: To create more authentic-looking, natural-functioning aquatic displays for our fishes. To understand and acknowledge  that our fishes and their very existence is influenced by the habitats in which they have evolved. 

We've mentioned ad nauseum here that wild tropical aquatic habitats are influenced greatly by the surrounding geography and flora of their region, which in turn, have considerable influence upon the population of fishes which inhabit them, and their life cycle. The simple fact of the matter is, when we add botanical materials to an aquarium and accept what occurs as a result-regardless of wether our intent is just to create a different aesthetic, or perhaps something more- we are to a very real extent replicating  the processes and influences that occur in wild aquatic habitats in nature.

The presence of botanical materials such as leaves in these aquatic habitats is foundational to their existence.


In the tropical species of trees, the phenomenon of "leaf drop" is hugely important to the surrounding environment. Vital nutrients are typically bound up in the leaves, so a regular release of leaves by the trees helps replenish the minerals and nutrients in the soils which are typically depleted from eons of leaching into the surrounding forests.

And the rapid nutrient depletion, by the way, is why it's not healthy to burn tropical forests- the release of nutrients as a result of fire is so rapid, that the habitat cannot process it, and in essence, the nutrients are lost forever.

Now, interestingly enough, most tropical forest trees are classified as "evergreens", and don't have a specific seasonal leaf drop like the "deciduous" trees than many of us are more familiar with do...Rather, they replace their leaves gradually throughout the year as the leaves age and subsequently fall off the trees.

So, what's the implication here?

There is a more-or-less continuous "supply" of leaves falling off into the jungles and waterways in these habitats, which is why you'll see leaves at varying stages of decomposition in tropical streams. It's also why leaf litter banks may be almost "permanent" structures within some of these bodies of water!

And, for the fishes and other organisms which live in, around, and above the litter beds, there is a lot of potential food, which does vary somewhat between the "wet" and "dry" seasons and their accompanying water levels. The fishes tend to utilize the abundant mud, detritus, and epiphytic materials which accumulate in the leaf litter as food. During the dry seasons, when water levels are lower, this organic layer compensates for the shortage in other food resources. 

During the higher water periods, there is a much greater amount of allochthonous input (remember that shit?) from the surrounding terrestrial environment in the form of insects, fruits, and other plant material. I suppose that, in our aquariums, it's pretty much always the "wet season", right? We tend to top off and replace decomposing leaves and botanical more-or-less continuously.

Now, of course, where is where I get into what I will call "speculative environmental biology!"

What if we stopped replacing leaves and even lowered water levels or decreased water exchanges in our tanks to correspond to, for example, the Amazonian "dry season" (June to December)? What impacts on the environmental parameters of our tanks would this have? And if you consider that many fishes tend to spawn in the "dry" season, concentrating in the shallow waters, could this have implications for stimulating breeding?

Could this be a re-thinking or re-imagining of how we spawn and rear some of our fishes?

I believe it might...

I think that we need to look a lot deeper into the idea of environmental manipulation for the purpose of getting our fishes to be healthier, more colorful, and especially, to spawn. Now I know, the idea is nothing new on a "macro" level- we've been increasing and lowering water temps in our aquariums, adjusting lighting levels, and tweaking environmental parameters to get fishes to spawn for a long time.

(Awesome pic by Mike PA Calnun)

Killie keepers have played with this concept in the drying and incubation periods in annual killifish eggs. That's some serious "next-level stuff" that's been done for a long time! Specific environmental manipulations for definitive results (ie; controlled egg hatching, etc.)

However, I don't think we've been doing a lot of real specific environmental adjusting water levels, increasing nutrient loads (ie; "pulsing" adding leaves and other botanicals), fostering biofilm growth, manipulating current, dissolved oxygen, food types, etc. for the expressed purpose of general husbandry and yeah- the spawning many other types of fishes.

I think that there are so many different things that we can play with- and so many nuances that we can investigate and manipulate in our aquariums to influence fish health and spawning behavior. I think that this could even add a new nuance to a typical biotope aquarium, such as creating an aquarium which simulates the "Preto da Eva River in Brazil in October", or whatever...with appropriate environmental conditions, such as water level, amounts of allochthonous material, etc.

Not just an aesthetic representation designed to mimic the look of the habitat- but a "functionally aesthetic" representation of a natural habitat, intended to operate like one..Full time.

Nuances. Micro-influences. Subtle steps. 

The possibilities are endless here! How do we start?

Well, we make those "mental shifts" and accept the dark water, the accumulation of leaves and botanicals, the apparent "randomness" of their presence. We study the natural habitats from which they come, not just for the way they look- but for WHY they look that way, and for how the impacts of the surrounding environments influence them in multiple ways.

Amano understood this. His disciples, if you will- IMHO seem to have dropped this in favor of mimicking his "look", while apparently disregarding his love of the processes which occur in Nature.

There is a tremendous amount of academic material out there for those willing to "deep dive" into this. And a tremendous amount to unravel and apply to our aquarium practices! We're literally just scratching the surface. We're making the shifts to accept the true randomness of Nature as it is.  We are establishing and nurturing the art of "functional aesthetics."

My real hope for the future? 

That one day, when some kid somewhere adds some specific combo of botanical materials to her wild Betta tank, for example, and someone asks why, she'll respond with something like, "Because these materials mimic the allochthonous inputs which occur in their wild habitats, and provide foraging and humic substances which will manipulate the aquarium environment and encourage the development of biofilms and other microorganisms for their long-term health" 

That's a mouthful. But, yeah...

Okay, I doubt some 11-year-old will respond exactly in those words- but I think that she'd suggest that the idea of using botanicals to do more than just create a pretty look in the aquarium is important. My hope is that this mindset will percolate into the consciousness of the general hobby, for the good of all who play with tropical fishes.

Not just for us obsessed weirdos!

Perhaps one day, among the things we indoctrinate neophyte aquarists to play with as fundamental skills, besides water exchanges, quarantine, and careful stocking, will be things like "...adding appropriate botanical materials to the aquarium to facilitate more natural conditions for the aquatic organisms we keep."

One can hope, right?

This is, indeed what we mean when we talk about how we operate at "The delta at the intersection of science and art."

You're there- because you're HERE.

This is the mission of Tannin Aquatics. That's the promise of the "botanical-style" aquarium. A pact with Nature, once forged by Amano, but evolved by a new generation of hobbyists, eager to replicate the form and function of Nature in their own aquariums as never before.

Study the natural. Embrace the ephemeral. Read about the philosophy of wabi- sabi, once taught by Amano, but seemingly forgotten in the quest for superficial aesthetics...Think of the possibilities. It starts with observing and studying nature.

And your aquarium.

Then, just add leaves, seed pods, bark, and twigs...And open your mind...

Amano himself, I think, would appreciate this. 

Yeah, I'm pretty certain that he would.

Okay, no further questions for today...I think I'll end up writing a damn book! But man, those were really GOOD questions, thanks! 

Until next time..

Stay curious. Stay thoughtful. Stay engaged. Stay diligent. Stay creative...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

November 14, 2019

Hi there!

I love the idea of introducing these organisms into our botanical-style tanks ahead of the fishes. You can obtain cultures of organisms like Daphnia, paramecium, etc. You can obtain pure cultures of these organisms from a place like my fave, Carolina Biological Supply ( You can even find Archaea there, too (we’ve written about them). And of course, you could even add stuff like worms, etc to your tanks to get a “live food” aspect going, too. A lot to do in this area!

Hope this helps!



November 12, 2019

You often write that in nature the leaf medium is a reservoir of food in the form of microorganisms, and what do you think about introducing these microorganisms into the aquarium? Do you have any idea for this? “Spontaneously” some microorganisms appear (Ostracoda, Hydra attenuata), but this is not much. How to introduce plankton into our aquariums?
best regards

Leave a comment