Hell? Or high water? Questions and answers on "The Urban Igapo" Concept...

Q- Hey Scott, LOVE the "Urban Igapo" idea, and have been doing a few of my own. Question, though, which I think about a lot...When do you know it's time to add water? Do you add it all at one time, or gradually? Thanks for all you do! -Rex

A- Thanks for the kind words, Rex! So, here's the deal: There is no real exact optimum time to flood your "igapo" or "varzea" setup. I suppose, if pressed, I'd tell you a good time is when the grassland terrestrial plants are growing at their strongest, with fairly dense coverage over the substrate, and when any terrestrial plants you've added are showing good growth.

If you want to mimic a natural cycle, you could do a bit of research on actual weather patterns in your target area..For example, The wet season in The Amazon runs from November to June. And it rains almost every day. So, you could add a little water every day, starting in November, and continuing on from there, right?

With grasses, like our beloved Paspalum, I wait until I have a pretty dense "carpet of the stuff, because it tends to fare better when submerged if it's growing strongly before I add the water.

I tend to add the water over the course of a few days (like 3-4), before reaching the desired depth. For whatever reason, I've found over the years that the grass tends to hang on longer under inundation when you add the water gradually. Maybe it gives the grass some time to "acclimate"; maybe it's just in my head, lol!

Q- Hi Scott! Having fun with the "igapo" thing, and loving "NatureBase!" Question for ya: How ya'll filter your tanks after you flood them? Can you get along without one? Curious! -Bridgett

A- Good one, Bridgett!  Most of my "Urban Igapo" tanks tend to be smaller, "nano-sized" affairs, 5 U.S. gallons or less. The options are to use a small hang-on power filter, a sponge filter, or...wait for it...NO FILTER! 


Think about it: We have a tank filled with rich soil, good grass or marginal plant growth (like my fave, Acorus), and typically in good light. It's entirely possible to manage the system without filtration. Depending upon the fishes you will add to the tank, it's not usually a problem. For example, I tend to play with a lot of annual or bottom-spawning killiefish in my "Urban Igapo" systems. These guys are traditionally kept, bred, and reared in small tanks, bowls, or other containers, without filtration. They're perfect for this sort of thing. 

Of course, you can keep other fishes, like Anabantids, which can be kept similarly (albeit in slightly warmer water), or even small characins, which also can do just fine in tanks with no filters for periods of time.

The key is to conduct regular water exchanges, don't overstock, and feed carefully.

Now, one caveat about filters in smaller "igapo" tanks: Because we tend to use sediment snd soil-based substrates, which can blow around a bit, be careful where you direct return flow, and how strong the return might be. Otherwise, you end up with a constantly turbid display, which might be annoying to some of you!


Q- Hey Scott. Really love the whole "flooded forest" idea, but I'm not sure if I want to do the whole "cycle" thing. Is it hard? And can I run mine differently?- Ray

Hello, Ray. Of course you can do it differently! There area lot of ideas to play with.

Now, it's been incredibly fun for me, 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.

Now, that's all well-and-good. We've kind of figured out how this wet-and-dry cycle can be managed in these types of systems. We're starting to really get this thing down, and it's easily replicated by the patient aquarist. We have a lot of blog posts and podcasts about the process, and we've even developed a line of substrates just for these types of systems!

However, let's think about simulating the "inundation season" as the aquarium. Let's assume that you're kind of not into doing the whole "start with a dry habitat, plant some grasses and terrestrial plants, and gradually inundate it with water, then gradually dry it out again" thing that is the crux  "Urban Igapo" idea.

You want to do things bait different. That's okay... There are lot of interesting possibilities for you.

So, if you're going "straight to the inundation phase" of the habitat in your tank, you can still take the approach of replicating the dry forest floor before adding  water. to the aquarium.  Run it dry for short period of time- even a week or so- before flooding. I'm sure you can do that!

By regularly wetting these materials- the substrate, leaves, botanicals, and wood- down for a few days, and letting them saturate, it's entirely possible to go from "terrestrial" to "aquatic" in a very short period of time, and getting the cool effect- and indeed, part the function (a burst of microbial life, biofilms, fungal growths, and release of tannin and humic substances) of this system from the start. 

At the risk of sounding crassly commercial, I'd recommend some sort of bacterial inoculant, such as our spray- on Purple Non-Sulphur Bacteria inoculant, "Nurture".-to "kick start" the biological processes in your system before it's inundated with water.

I think that this step of "bacterial inoculation" is such a fundamental part of the botanical-style aquarium approach. I see it as much less of a "hack" to kick-start the nitritogen cycle (it will help do that...) and more of a way to provide an initial population of life forms which help assimilate some of the botanical materials and make the many organic (and other) compounds and substances locked in their tissues (tannins, humic substances, lignin, sugars, etc.) available to other life forms within the evolving microcosm you're creating.

So, yeah...I got a bit carried away there, but you CAN take some different approaches to this stuff...It's all very "ground floor",with lotto learn and do!

I hope that these selections from our email will answer some of your questions on this fun and exciting new way to run a unique and dynamic aquarium!

Stay excited. Stay creative. Stay observant. Stay bold...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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