Considering the seasons...

The botanical-style aquarium challenges us. 

It forces us to look at things a bit differently. To accept a different look, a different function, and to embrace Nature in a more intimate way in our aquariums that we typically do.

And, in order to make sense of it all, we spend a great deal of time examining the processes which occur when leaves and other botanicals are added to the aquarium.

And this is important, not only from an aesthetic standpoint, but from a functional/operational standpoint.

It definitely differs from our hobby practice in decades past, where the idea of throwing in materials that affect the water quality/composition was strictly a practice reserved for speciality hobbyists, like killifish breeders, Dwarf Cichlid keepers, etc., who wanted to create special conditions for breeding.

Nowadays, we're advocating the addition of such materials to our aquariums as a matter of course, for the everyday purpose of replicating natural processes for our fishes. We understand- or are attempting to understand- the impact on both our aquariums' ecology and the husbandry involved.

Yeah, sort of a different approach.

We add a lot of biological material to our tanks in the form of leaves and botanicals- perfectly analogous to the process of allochonous inputmaterial is something imported into an ecosystem from outside of it. Exactly what happens in the tropical streams and rivers that some of us obsess over!

There's been a fair amount of research and speculation by both scientists and hobbyists about the processes which occur when terrestrial materials like leaves and botanical items enter aquatic environments, and most of it is based upon field observations.

As hobbyists, we have a unique opportunity to observe firsthand the impact and affects of this material in our own aquariums! I love this aspect of our "practice", as it creates really interesting possibilities to embrace and create more naturally-functioning systems, while possibly even "validating" the field work done by scientists!

And of course, there are a lot of interesting bits of information that we can interpret from Nature when planning, creating, and operating our aquariums.

It goes without saying that there are implications for both the biology and chemistry of the aquatic habitats when leaves and other botanical materials enter them. Many of these are things that we as hobbyists observe every day in our aquariums!


A lab study I came upon found out that, when leaves are saturated in water, biofilm is at it's peak when other nutrients (i.e.; nitrate, phosphate, etc.) tested at their lowest limits. This is interesting to me, because it seems that, in our botanical-style, blackwater aquariums, biofilms tend to occur early on, when one would assume that these compounds are at their highest concentrations, right? And biofilms are essentially the byproduct of bacterial colonization, meaning that there must be a lot of "food" for the bacteria at some point if there is a lot of biofilm, right?

More questions...

Does this imply that the biofilms arrive on the scene and peak out really quickly; an indication that there is actually less nutrient in the water? Is the nutrient bound up in the biofilms? And when our fishes and other animals consume them, does this provide a significant source of sustenance for them?


Oh, and here is another interesting observation:

When leaves fall into streams, field studies have shown that their nitrogen content typically will increase. Why is this important? Scientists see this as evidence of microbial colonization, which is correlated by a measured increase in oxygen consumption. This is interesting to me, because the rare "disasters" that we see in our tanks (when we do see them, of course, which fortunately isn't very often at all)- are usually caused by the hobbyist adding a really large quantity of leaves at once, resulting in the fishes gasping at the surface- a sign of...oxygen depletion?

Makes sense, right? 

These are interesting clues about the process of decomposition of leaves when they enter into our aquatic ecosystems. They have implications for our use of botanicals and the way we manage our aquariums. I think that the simple fact that pH and oxygen tend to go down quickly when leaves are  initially submerged in pure water during lab tests gives us an idea as to what to expect.

A lot of the initial environmental changes will happen rather rapidly, and then stabilize over time. Which of course, leads me to conclude that the development of sufficient populations of organisms to process the incoming botanical load is a critical part of the establishment of our botanical-style aquariums.

Fungal populations are as important in the process of breaking down leaves and botanical materials in water as are higher organisms, like insects and crustaceans, which function as "shredders." So the “shredders” – the animals which feed upon the materials that fall into the streams, process this stuff into what scientists call “fine particulate organic matter.”

And that's where fungi and other microorganisms  make use of the leaves and materials, processing them into fine sediments. Allochthonous material can also include dissolved organic matter (DOM) carried into streams and re-distributed by water movement.

And the process happens surprisingly quickly.

In experiments carried out in tropical  rainforests in Venezuela, decomposition rates were really fast, with 50% of leaf mass lost in less than 10 days! Interesting, but is it tremendously surprising to us as botanical-style aquarium enthusiasts? I mean, we see leaves begin to soften and break down in a matter of a couple of weeks- with complete breakdown happening typically in a month or so for many leaves. And biofilms, fungi, and algae are still found in our aquariums in significant quantities throughout the process.

So, what's this all mean? What are the implications for aquariums? 

I think it means that we need to continue to foster the biological diversity of animals in our aquariums- embracing life at all levels- from bacteria to fungi to crustaceans to worms, and ultimately, our fishes...All forming the basis of a closed ecosystem, and perhaps a "food web" of sorts for our little aquatic microcosms. It's a very interesting  concept- a fascinating field for research for aquarists, and we all have the opportunity to participate in this on a most intimate level by simply observing what's happening in our aquariums every day!

Diversity is interesting enough, but when you factor in seasonal changes and cycles, it becomes an almost "foundational" component for a new way of running our botanical-style aquariums.

Consider this:

The wet season in The Amazon runs from November to June. And it rains almost every day.

And what's really interesting is that the surrounding Amazon rain forest is estimated by some scientists to create as much as 50% of its own precipitation! It does this via the humidity present in the forest itself, from the water vapor present on plant leaves- which contributes to the formation of rain clouds.

Yeah, trees in the Amazon release enough moisture through photosynthesis to create low-level clouds and literally generate rain, according to a recent study published in the Proceedings of the National Academy of Sciences (U.S.)!

That's crazy.

But it makes a lot of sense, right?

Okay, that's a cool "cocktail party sound bite" and all, but what happens to the (aquatic) environment in which our fishes live in when it rains?

Well, for one thing, rain performs the dual function of diluting organics, while transporting more nutrient and materials across the ecosystem. What happens in many of the regions of Amazonia - and likewise, in many tropical locales worldwide-is the evolution of our most compelling environmental niches...

The water levels in the rivers rise significantly- often several meters, and the once dry forest floor fills with water from the torrential rain and overflowing rivers and streams. In Amazonia, it means one thing:

The Igapos are formed. 

All of the botanical material- fallen leaves, branches, seed pods, and such, is suddenly submerged. And of course, currents re-distribute this material into little pockets and "stands", affecting the (now underwater) "topography" of the landscape. Leaves begin to accumulate. Tree branches tumble along the substrate  Soils dissolve their chemical constituents, tannins, and humic acids into the water, enriching it. Fungi and micororganisms begin to multiply, feed on and break down the materials. Biofilms form, crustaceans reproduce rapidly.  Fishes are able to find new food sources; new hiding areas to spawn.

Life flourishes.

So, yeah, the rains have a huge impact on tropical aquatic ecosystems. And it's important to think of the relationship between the terrestrial habitat and the aquatic one when visualizing the possibilities of replicating nature in your aquarium in this context.

This is huge, important stuff that any real "natural aquascaping" enthusiast needs to get his/her head around. 

It's an intimate, interrelated, and perhaps even "codependent" sort of arrangement!

And of course, I think we can work with this stuff to our fishes' advantage!

We've talked about the idea of "flooding" a vivarium-type setup designed to replicate an Amazonian forest before. You know, sort of attempting to simulate some of the processes which happen seasonally in Nature. With the technology, materials, and information available to us today, the capability of creating a true "year-round" habitat simulation in the confines of an aquarium/vivarium setup has never been more attainable.

The time to play with this concept is now!

Sure, you'd need to create a technical means or set of procedures to gradually flood your "rainforest floor" in your tank, which could be accomplished manually, by simply pouring water into the vivarium over a series of days; or automatically, with solenoids controlling valves from a reservoir beneath the setup, or perhaps employing the "rain heads" that frog and herp people use in their systems. This is all very achievable, even for hobbyists like me with limited "DIY" skills.

You just have to innovate, and be willing to do a little work and experimentation.

And, you have to accept some new and very different aesthetics. You have to understand that when you flood a soil/clay/sediment-based substrate with water, it's going to be turbid. It's going to not be crystal clear and "aquarium culture perfect" in appearance.

When you make the mental shifts, you can just ponder the possibilities here! It's crazy!

As the display "floods", the materials in the formerly "terrestrial" environment become submerged- just like in Nature- releasing nutrients, humic substances, and tannins, creating a rich, dynamic habitat for fishes, offering many of the same benefits as you'd expect from the wild environment.

Recreating a "365 dynamic" environment in an aquatic feature would perhaps be the ultimate expression of an operational biotope-inspired aquarium- Truly mimicking the composition, aesthetics- and function of the natural habitat. A truly realistic representation of the wild, on a level previously not possible.

No more of that "diorama" bullshit.

Of course, I have no illusions about this being a rather labor-intensive process, fraught with a few technical challenges- but it's not necessary to make it complicated or difficult.

You'll have to be patient and make smaller, slower, incremental moves...I mean, you're starting out with a "dry" aquarium- a representation of a forest floor or grassland, letting it thrive- and then flooding it.

It does require some "active management", planning, and diligence- but on the surface, executing seems no more difficult than with some of the other aquatic systems we dabble with, right?

The transformation of dry forest floors into aquatic habitats provides a tremendous amount if inspiration AND biological diversity and activity for both the natural environment and our aquariums.

As always, it's best to look to Nature for your inspiration. You simply won't find much in the way of aquariums created to replicate these habitats and processes just yet.

And, man- Nature provides some really incredible inspiration for this stuff, doesn't it?

Flood pulses in these habitats easily enable large-scale "transfers" of nutrients and food items between the terrestrial and aquatic environment. This is of huge importance to the ecosystem. As we've touched on before, aquatic food webs in the Amazon area (and in other tropical ecosystems) are very strongly influenced by the input of terrestrial materials, and this is really an important point for those of us interested in creating more natural aquatic displays and microcosms for the fishes we wish to keep.

Characins, catfishes, dwarf cichlids, annual killifish- all have unique relationships with these habitats, which we can replicate, study, and interpret. They respond to the seasonal changes almost predictably.

And the seasonality in these wild aquatic habitats is perhaps the one feature that we as aquarists have yet to fully embrace and study. It's fascinating, intriguing...and dramatic, in many cases!

What can we learn from these seasonal inundations?

Well, for one thing, we can observe the diets of our fishes.

In general, fish, detritus and insects form the most important food resources supporting the fish communities in both wet and dry seasons, but the proportions of invertebrates fruits, and fish are reduced during the low water season. Individual fish species exhibit diet changes between high water and low water seasons in these interesting adaptation and possible application for hobbyists?

Well, think about the results from one study of gut-content analysis form some herbivorous Amazonian fishes in both the wet and dry seasons: The consumption of fruits in Mylossoma and Colossoma species was significantly less during the low water periods, and  their diet was changed, with these materials substituted by plant parts and invertebrates, which were more abundant.

Fruit-eating is significantly reduced during the low water period when the fruit sources in the forests are not readily accessible to the fish. During these periods of time, fruit eating fishes ("frugivores") consume more seeds than fruits, and supplement their diets with foods like as leaves, detritus, and plankton. Interestingly, even the known "gazers", like Leporinus,  were found to consume a greater proportion of materials like seeds during the low water season.

Mud and algal growth on plants, rocks, submerged trees, etc. is quite abundant in these waters at various times of the year. Mud and detritus are transported via the overflowing rivers into flooded areas, and contribute to the forest leaf litter and other botanical materials, coming nutrient sources which contribute to the growth of this epiphytic algae. 

During the lower water periods, this "organic layer" helps compensate for the shortage of other food sources. When the water is at a high period and the forests are inundated, many terrestrial insects fall into the water and are consumed by fishes. In general, insects- both terrestrial and aquatic, support a large community of fishes.

So, it goes without saying that the importance of insects and fruits- which are essentially derived from the flooded forests, are reduced during the dry season when fishes are confined to open water and feed on different materials. 

So I part of the key to successfully conditioning and breeding some of the fishes found in these habitats altering their diets to mimic the seasonal importance/scarcity of various food items? In other words, feeding more insects at one time of the year, and perhaps allowing fishes to graze on detritus and biocover at other times?

Is the concept of creating a seasonally-influenced,  "food-producing" aquarium, complete with detritus, natural mud, and an abundance of decomposing botanical materials, a key to creating a more true realistic feeding dynamic, as well as an "aesthetically functional" aquarium?

I'm fairly certain that this idea will make me even less popular with some in the so-called "Nature Aquarium" crowd, which, in my opinion, has sort of appropriated the descriptor while really embracing only one aspect of nature (i.e.; plants)...Hey, I love the look of many of those tanks as much as anyone...but let's face it, a truly "natural" aquarium needs to embrace stuff like detritus, mud, decomposing botanical materials, varying water tint and clarity, etc.

If you are intrigued by that, and not frightened of the looks and operational considerations, you'll love NatureBase "Igapo" substrate. After over a year of testing, it's now weeks away from release...It'll challenge you. It'll create turbidity. It'll color the water. It'll grow terrestrial grasses. It will foster biofilm formation. It'll get your creative juices flowing. 

And we think it will reinforce the idea of what we mean by "functional aesthetics."

The aesthetics might not be everyone's cup of tea, but the possibilities for creating more self-sustaining, ecologically sound microcosms are numerous, and the potential benefits for fishes are many. Creating aquariums based on specific natural functions and benefits is something that I can't resist.

And, since a few of you asked...THAT is where Tannin is headed in the second half of 2020 and into next year. A new approach. A different look, products that might have you scratching your head in sheer terror AND delight! We're going to do a lot more pushing out into the margins of what is considered "normal" in the hobby. 

And that's just where we like to be.

Stay excited. Stay focused. Stay inspired. Stay creative. Stay tuned...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

June 21, 2020

Hey Luke,

We are actually cultivating a few and are looking at ramping up production to levels that we can male it practical to sell some. Likely we will sell the grasses in seed form (they’re ridiculously easy to sprout), and perhaps some of the hardier plants in sported form, and eventually, mangrove propagules (we’ve sold those before, too…). Yeah, working on it! 🤓


luke casteel
luke casteel

June 19, 2020

quick question:
do you think you would be able to sell a small variety of terrestrial grasses here on tannin?
(; i think that would be totally radical and would really help to simplify the whole urban igapo process…
but if not ill still figure it out

Leave a comment