March 08, 2021

The Urban Igapo in practice...

It's been about 4 years since we first presented our idea for replicating the flooded forests and meadows of South America (Igapo and Varzea).

In a fun homage to the hobby, we called the concept the "Urban Igapo." About 2 years ago, we went more in depth with some of the procedures and techniques that you'd want to incorporate into your executions of the idea.

Here are some answers to a few of the most common questions we receive on the idea.

Do I have to have a "dry season?"

Well, that's a good question! I mean, the whole idea of this particular approach is to replicate as faithfully as possible the seasonal wet/dry cycles which occur in these habitats. It starts with a dry or terrestrial environment, managed as such for an extended period of time, which is gradually flooded to simulate inundation which occurs when the rainy season commences and swollen rivers and streams overflow into the forest or grassland.

Sure, you can replicate the "wet season" only- absolutely. I've seen tons of tanks created by hobbyists to do this. However, if you want to replicate the seasonal cycle- the real magic of this approach- it's more fun to do the "dry season!"

Think of it in the context of what the aquatic environment is- a forest floor or grassland which has been flooded. If you develop the "hardscape" (gulp) for your tank with that it mind, it starts making more sense. What do you find on a forest floor or grassland habitat? Soil, leaf litter, twigs, seed pods, branches, grasses, and plants.

Just add water, right?

What size aquarium do you need?

You can use just about any size of aquarium. Most of my executions have been in smaller tanks (1-10 U.S. gallons). Of course, you can scale this up to medium and large aquariums. The concept is the same.The execution is the same. The biggest challenge, in my opinion, is embracing the fact that you might set up a large tank which may not have any fishes in it for months. Patience! It's a mental shift; a commitment to following though on an idea that is rather "alien" to most aquarists.

Does the grass and plants that you've grown in the "dry season" survive the inundation?

Another great question. Some do, some don't. (How's that for concise info!). I've played with grasses which are immersion tolerant, such as Paspalum. This stuff will "hang around" for a while while submerged for about a month and a half to two months, in my experience, before ultimately succumbing. Sometimes it comes back when the "dry season" returns. However, when it doesn't survive, it decomposes in the now aquatic substrate, and adds to the biological diversity by cultivating fungi and bacteria.

You can use many plants which are riparian in nature or capable of growing emmersed, such as my fave, Acorus, as well as all sorts of plants, from Hydrocotyle, Cryptocoryne, and others. These can, of course, survive the transition between aquatic and "terrestrial" environments.

How long does the "dry season" have to last?

Well, if you want to mimic one of these habitats in the most realistic manner possible, follow the exact wet and dry seasons as you'd encounter in the locale you're inspired by. Alternatively, I'd at least go 2 months "dry" to encourage a nice growth of grasses and plants prior to inundation.

And of course, you cans do this over and over again!

When you flood the tank, doesn't it make a cloudy mess? Does the water quality decline rapidly?

Sure, when you add water to what is essentially a terrestrial "planter box", you're going to get cloudiness, from the sediments and other materials present in the substrate. You will have clumps of grasses or other botanical materials likely floating around for a while.

Surprisingly, in my experience, the water quality stays remarkably good for aquatic life. Now, I'm not saying that it's all pristine and crystal clear; however, if you let things settle out a bit before adding fishes, the water clears up and a surprising amount of life (various microorganisms like Paramecium, bacteria, etc.) emerges. Curiously, I personally have NOT recorded ammonia or nitrite spikes following the inundation. That being said, you can and should test your water before adding fishes. You can also dose bacterial inoculants, like our own "Culture" or others, into the water to help.

Should I use a filter in the "wet season?"

You certainly can. I've gone both ways, using a small internal filter or sponge filter in some instances. I've also played with simply using an air stone. Most of the time, I don't use any filtration. I just conduct partial water exchanges like I would with any other tank- although I take care not to disturb the substrate too much if I can. When I scale up my "Urban Igapo" experiments to larger tanks (greater than 10 gallons), I will incorporate a filter.

What kinds of fishes can you keep in these systems?

I've played with a lot of different types of fishes. Particularly annual killifishes, small characins (like Red Phantom Tetras, Neons, and others), Gouramis, and Bettas. Lots of possibilities!