February 09, 2021

The ever-growing inspiration of the morichal

One of my favorite parts of the aquarium hobby is learning about different aquatic habitats, and considering the ecology and the fishes which reside in them. This of course, gives me a lot of inspiration for new aquarium executions. That's what keeps this hobby so amazing!

I'm totally fascinated by the floodplain rivers and wetland complexes from which many of our aquarium fishes come. Most of these habitats are subject to extensive seasonal flooding. Large river channels possess well-developed fringing floodplain systems, such as the "internal delta", located at the confluence of the Apure and Orinoco.

A "morichal" is a lowland stream found in Savannah areas of South America, Amazon River basin, the upper Negro River drainage in Brazil, the Orinoco River basin, and along the Orinoco River in Colombia and Venezuela, among other locales. The habitat is dominated by a certain type of palm tree, the "Moriche Palm" (Mauritia flexousa), and extensive riparium vegetation. This palm only grows were its roots can be underwater (love that!),and typically is found in groups- hence the term, "morichal", which refers to...a group of them!

These are surprisingly densely populated habitats, fish wise. Morichals are characterized as having what ecologists call "High structural complexity". The two types of morichal habitats are flooded vegetated areas and "sandbanks." The flooded vegetated areas are dominated by stands of the aforementioned "Moriche palm", having up to 90% substrate coverage, consisting of large woody debris derived from riparian vegetation (mainly the palms), as well as terrestrial grass and leaf litter. These habitats have a very moderate or slow current (< 0.05 m/s) and depth (3ft/ 1 m or less).

"Sandbanks" in the morichal are defined as sandy beaches off of the main channels (mostly comprised of coarse sand substrate) with depth of around 3ft/ 1 m, and moderate current (< 0.06 m/s).

Morichals are considered important systems for the maintenance of freshwater Neotropical fauna in lowland savannas. The monodominant stands of the palm and associated growths provide important food to a great number of species,

Although typically supplied with underground water sources throughout the year, these streams swell with water during periods of seasonal flooding. Riparian vegetation and sandy substrates abound. And when you have trees, vegetation, and seasonal influx of water, utilizing botanicals in your aquarium replication of this habitat is just "par for the course', right?

The habitat itself has an abundance of botanical debris, leaves, macro algae, fallen branches, palm fronds, and a matrix of roots and such. And, with terrestrial plants growing right up to the water's edge, the possibilities to create a cool aquatic display are unlimited! With a little creativity, one could simulate the growth of the riparian vegetation of the "morichal."

The flooded vegetation habitats along most morichals are important to fish fauna, composed largely of small-bodied cichlids, characins, lebiasinids, and silurids. The sand patches tend to have slightly less species richness and population density than the vegetated areas.

It makes sense that the vegetated habitats are more populous, right? I mean, these littoral habitats, which contain woody debris and leaf litter are known by ecologists to support higher "primary and secondary productivity" which provides fishes with more foraging opportunities on a larger variety of substrates.

Again, it's a case of the fishes following the food- an idea we've discussed many times here, right? 🤓

In a study I found of a typical morichal habitat by authors Carmen G. Montaña, Craig A. Layman, and Donald C. Taphorn, the distribution of fishes among the two major morichal habitats was explained as follows:

"...in vegetated patches we found a relatively high abundance of small cichlids and doradid catfishes with different body shapes and feeding habits (e.g., Apistgramma hoignei, Physopyxis ananas). But small omnivorous characids with less-diversified body morphologies (Characidae), such as tetras of the genera Moenkhausia spp. and Hemigrammus spp., dominated open and shallow beaches."

And this little tidbit from the study is quite interesting, too: "Although we did not evaluate communities of small invertebrates in this study, it was apparent that vegetated patches contained a high abundance of shrimps and other macroinvertebrates."

Yeah, shrimp.

Oh, and aquatic plants, too!

It is not uncommon to find large stands of Eleocharis in shallow areas. In the deeper water, several species of Ludwigia are found in significant density, and in the shallows, you'll often find simple filament algae. Another cool aquatic plant that you'll find in these habitats stats is the much-loved (yet challenging to many) Tonina fluviatilis, which grows in dense stands within these shallow, acidic, slow-moving morichal habitats.

Although the waters in these habitats are largely clear (as in, not turbid), some are stained with tannins and are typically acidic in pH (usually 6.0 or less), and have a significant amount of roots and such from the terrestrial and riparium vegetation surrounding. You'll find lots of palm leaves, fruits, and seed pods submerged on the substrate in morichals.

And of course, that's where we come in, right?

Scattering botanicals materials along the bottom of the aquarium would create a pretty good replication of the morichal environment! I would probably not go too crazy, in terms of variety; rather, I'd limit my selections to a few botanicals and just sort of "do it up" that way, so as to emphasize the abundance of several dominating terrestrial plant species in the locale.

"What about the fishes, Scott?"

Oh, yeah!

These environments often contain dozens of different fish species in relatively small areas, including characins, catfishes, and dwarf cichlids. Unusual characin species, such as Hemiodus, are often found in these habitats. Occasionally available in the aquarium trade, they would make really cool "stars" for a specialized display like this! The lovely "Green Neon Tetra" (Paracheirodon simulans), is a known (and super sexy!) denizen of this habitat, as well!

Oh, and Dwarf Pike Cichlids are often found in morichal habitats...hello!

Of course, some of the more popular characins, such as Pencilfishes (N. unifasciatus is notable), are found there. And Apistogramma, along with the beloved Mesonauta insignis, are found in morichals, which will lend a familiar, if not somewhat exotic look to your display!

As a subject for a riparium study, the morichal environment presents a near-perfect opportunity to stretch your aquatic creativity, while highlighting some well-known fishes in an unusual and not-often-replicated niche.

Think of the creative possibilities here!

The morichal is symbolic of where we are in the aquarium hobby: At a real "high point", where it's entirely possible to create realistic, "functionally aesthetic" aquatic display utilizing natural materials to mimic the look and feel of the amazing aquatic habitats of the world, while simultaneously learning about these priceless natural treasures.

With so much to explore in the natural world, and so many habitats- or aspects of them- to replicate in the aquarium, we have unique opportunities to get out of our "comfort zones", study the form and function of them, and create great work. It will be really fun to see what kinds of representations our community will continue to push out to the world.

Let's keep pushing!

Stay creative. Stay studious. Stay bold. Stay excited...

And Stay Wet.

Scott Fellman

Tannin Aquatics