It's raining life in the "urban igapo."

Land and water...

If there's one consistent lesson in what we do, it's that land and water are inexorably linked together. And I think that when we contemplate the dynamic of how water and the aquatic environment interact, it makes us look at aquatic habitats- and our aquariums-a bit differently.

And it starts with...rain.

And I like rain.

"I'm only happy when it rains
I'm only happy when it's complicated
And though I know you can't appreciate it
I'm only happy when it rains..."

- From the song, "I'm Only Happy When it Rains" by Garbage, 1993


Yeah, rain is cool. 

And, of course, today's topic allowed me to quote lyrics from an obscure, yet satyrical post-punk song from one of the better bands of the 90's...

We're off to a great start, I think!

So, it goes without saying that one of the most essential and life-giving processes of our planet is weather. And one of the most important components of weather is rain. 

Rain is truly the bearer of life. It's transformational, essential for our existence...and for the continued existence of many of the fishes we love, as well as the habitats from which they come.

And specifically, what interests me about rain is what happens when it rains in the wild habitats of our fishes. How do their habitats change with the coming and going of the rains?  

What happens to the fishes during the rainy season?

I know, you're gonna say, "They get wet..." 

Look, no one likes a freaking smart ass, okay? :)

Consider what happens in the "rainy season" in say, the Amazon Basin.

"What would that be, Scott?"

A lot of things, really.

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! Think about THAT for a minute. 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?

Yet another reason why we need to protect these precious habitats. You cut down a tree in the Amazon- you're literally reducing the amount of rain that can be produced.

It's that simple.

That's really important. It's more than just a cool "cocktail party sound bite."

So what happens to the (aquatic) environment in which our fishes live in when it rains? What does the rain actually do?

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, for example- 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.

The Igapos are formed. 

Flooded forest floors.

The formerly terrestrial environment is now transformed into an earthy, twisted, incredibly rich aquatic habitat, which fishes have evolved over eons to live in and utilize for food, protection, and spawning areas.

All of the botanical material-shrubs, grasses, fallen leaves, branches, seed pods, and such, is suddenly submerged; often, currents re-distribute the leaves and seed pods and branches into little pockets and "stands", affecting the (now underwater) "topography" of the landscape.

Leaves begin to accumulate.

Soils dissolve their chemical constituents- tannins, and humic acids- into the water, enriching it. Fungi and micororganisms begin to feed on and break down the materials. Biofilms form, crustaceans multiply 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.

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

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

We've talked about the idea of "flooding" an aquarium 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!

We've been testing the idea for a long time, and have been formulating some soils which attempt to replicate some of the attributes of those found in these habitats during the "dry" season. When flooded, you get an effect that's similar to what happens in the igapo.

Sure, the water gets cloudy for a bit. The water is tinted, turbid, and sediment-laden. Eventually, it settles out. If you planted grasses and plants which are able to tolerate submersion for some period off their life cycle, they'll "hang on" for a while- until the waters recede. Just like in Nature.

To replicate this process is really not difficult. It mimics the "dry start" method that many aquatic plant enthusiasts play with. Except our goal isn't to start plants for a traditional aquarium. It's to replicate, on some levels, the year-round dynamic of the Amazonian forests. We favor terrestrial plants- and grasses-grown from seed, to start the "cycle." SO, those of you who are ready to downplay the significance of experimenting with this stuff because "people have done 'dry start' planted tanks for years" , take comfort in the fact that I recognize that, and acknowledge that we're taking a slightly different approach here, okay?

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 busy work. You can keep it incredibly simple, and just utilize a small tank. You must be patient.

Or, you can purchase an off-the-shelf product like the Biopod, which our friend Paulie Dema of Vivariums in the Mist in New York has used to create some amazing setups, some incorporating our botanicals! 

Think about the possibilities here. Not just for unique aesthetics, either.

As the display "floods", the materials in the formerly "terrestrial" environment become submerged- as in nature- releasing nutrients, humic substances, and tannins, creating a rich, dynamic habitat for fishes. 

Again, we have the opportunity to recreate aspects of this dynamic in both form and function.

Recreating a "365 dynamic" in an aquatic feature would perhaps be the ultimate expression of a functional biotope-inspired  aquarium- mimicking the composition, aesthetics- and the ecological/biological functions of the natural habitat. A truly realistic representation on a level previously not embraced.

Now, I have no illusions about this being a rather slow, perhaps even labor-intensive process, but it's not necessary to make it complicated or difficult.

It requires 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!

Like, hello- reef tanks, for example! Or vivariums.

Sure, you'd have to make some provisions for "relocating" the terrestrial inhabitants of your system, like frogs, to "higher ground" (i.e.; another vivarium) during the "wet season"...or your could create a paludarium-type setup, with both a terrestrial and an aquatic component simultaneously...

As mentioned above, you'll have to deal with some "aesthetic challenges"- the likes of which you haven't before- as you "flood" the system. The turbidity, biofilms, decomposition, deeply tannin-stained water...Stuff that we as botanical-style aquarium enthusiasts are already pretty well "trained" to accept and embrace.

One could even represent various "phases" of the inundation, as I have done in one of my latest aquariums. Not everyone's cup of tea...but remarkably similar to what you see in Nature during the latter part of the inundation cycle, where terrestrial vegetation is largely dormant, and only lingering turbidity and a smattering of living vegetation remains.


The possibilities for education, creative expression, and experimentation are really wide open here! 

And of course, you're certainly not limited to the igapo (blackwater flooded forests) and varzea ("whitewater" flooded forests) of South America. There are numerous other habitats around the world which you could replicate on some level.

One could mimic all sorts of geographic locales and niche habitats, including those found in Africa and Southeast Asia.

Annual killifish would be another beneficiary of such a process/system, with the ability to literally "desiccate" their environment for the "dry season", and flood it once again when "the rainy season" returns! We kind of do it already with the old "peat moss in a bag" trick to incubate their eggs...this is just a more interesting (and probably a bit more tedious/less efficient) way to do it...but one which may yield interesting insights into their natural habitats and behaviors!

There are so many possibilities here...Well- it literally could create an entirely new "sub-hobby" within the aquatic hobby...not just biotope replication- biotope "operation!" The idea of a "365 Dynamic Aquatic Display"- what we've dubbed the "Urban Igapo"- has never been more approachable! And you can, as the name implies- recreate it in the comfort of your own home.

I'm just gonna stop here, because I could easily go on and on and on....

Think about it. Build it. Play with it. Learn from it. Share it.

Stay fascinated. Stay creative. Stay excited. Stay imaginative. Stay observant. Stay patient. Stay open-minded...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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