Opposite directions: Two little "case studies" on the influence of underwater nuances

As aquarists, we spend a good part of our time trying to figure out how to keep our fishes healthy and happy.  And as dedicated natural aquarium enthusiasts, we take it a level deeper, and try to re-create as many of the features of our fishes' natural habitats as possible.

Today, we're going to take the most cursory of looks at two unique habitats- pretty much polar opposites of each other- to facilitate the idea of topography and its influence on the aquatic environment. By studying these habitats, we're seeing for ourselves the unique possibilities that are out there to work into the aquarium.

And I think it goes beyond just creating a cool-looking habitat with wood or botanicals or rock, and calls upon us to investigate other factors, such as the currents and underwater topographic features of these ecosystems. It's about exploring how these features affect the life habits of our fishes.

There is a reason why fishes aggregate and live out their lives in specific environmental niches; and it goes beyond just the presence of leaves, or the acidity or alkalinity of the water.

The physical structures and flow patterns which make up the streams, rivers, and other aquatic habitats are a fascinating study in and of themselves. And yeah, there are many different habitats where physical barriers in the water affect the underwater environment.


For example, I'm fascinated by what stream ecologists call "riffles" (defined as shallow sections of a stream with rapid current and a surface broken by gravel, rubble or boulders), with a moderately-fast-flowing current and mostly sandy bottom with tree roots, leaves, driftwood pieces, and small rocks and pebbles. (ohh...home to Darter Characins! I'm thinking cool niche biotope aquarium here...)

These "riffles" are considerably more significant in the wet season, when the obvious impact of higher water volumes are present. They're fascinating habitats to explore- and interesting to replicate in our aquariums!


In many aquatic habitats, riffles have  well-defined margins and barriers which divert and alter water flow patterns. Often, these features are created by stuff like fallen trees or branches, and become semi-permanent or even permanent features to the underwater 'landscape."

And interestingly, in South America, you'll find an unexpected abundance of some species familiar to us as hobbyists in these "riffles."

Some scientists have postulated that the higher presence of nocturnal predators in the pools adjacent to the more active riffles might increase the number of species that seek refuge in the riffles to avoid them!

Fishes like Rivulus, which usually live in more intermittent pools along the stream edges, outside the main stream channels, are normally found at night in these riffles!  So, protection from predators- survival- is a powerful motivation for fishes to seek out these different habitats. Now, granted, in the aquarium we are almost guaranteed NOT to keep predators and prey in the same tank (at least, not for long-term display purposes!), but is there not something to be gained by replicating such environments? 


Reduction of stress. Fostering of natural behaviors...Even if they are not "necessary" for survival. I can't hope but wonder if providing some of these more specific environmental conditions (in concert with stuff like water chemistry and the presence of stuff like leaves, wood, etc.) could facilitate greater possibilities for spawning, long-term health, and greater lifespan?


I think it's entirely possible. I think we need to look beyond just the cool looks of the natural habitats from where our fishes hail. It's a "complete package" sort of thing.

Application of water movement-something we've embraced in reef aquariums for decades to facilitate natural responses and long-term health in our animals- has its place in almost every type of natural aquarium, doesn't it?


I'm thinking that it does.

So, dust off those powerheads. Reconsider the way you return water to your aquarium. Evaluate the underwater "topography" of the natural environments and the life habits of your fishes from these locales. 

Further, re-think how stuff like lighting patterns, rain, etc., influence our fishes. Consider how we might apply this information to better the lives of the fishes in our aquariums. These types of nuances play an important role in helping us re-create some of the more interesting aquatic habitats of the world. 


Let's go in the opposite direction now: The fascinating, sluggish, lagoon-like habitats of South America known as "morichals."

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 underwate (love that!),and typically is found in groups- hence the term, "morichal", which refers to...a group of them!

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, ranging from Monkeys to birds to of course, fishes.

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 and submerged terrestrial grasses, along with the unique underwater topography of the "morichal." 

And, incorporating riparian plants in our displays is something we've talked about and toyed with here for some time.

I've cultivated some riparian plants, such as Acorus, for the past couple of years, which "I'm gonna" use someday in a paludarium-type replication of this habitat! A paludarium would open up some unique aesthetic opportunities to really push the boundaries of creativity!

In the past, I've even experimented with small "Cat Palms" (Chamaedorea cataractarum) and rooted them in leaf-strewn, shallow sand substrates- a sort of "micro morichal" setup! I know this concept can work! Further experimentation in this area can no doubt yield some cool results!

And of course, whenever you have these rather complex physical habitats, you end up with a diversity of life and food sources- and hence, fishes which are suited to exploit them. This interesting summary from a study I encountered on Morichal habitats expands upon this:

"In structurally complex habitats, specialist species also can exploit specific food resources to which they are morphologically or physiologically adapted to utilize (Willis et al., 2005). For example, 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.

Littoral habitats containing woody debris and leaf litter also might support higher primary and secondary productivity which provides fishes with more foraging opportunities on a larger variety of substrates (Benke et al., 1985; Crook & Robertson, 1999). Relationships between fish structure and macroinvertebrate assemblages have been associated with habitat heterogeneity (Angermeier & Karr, 1984)."

Although the waters in these habitats are largely clear (as in, not turbid), they 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. And there is not a huge amount of water movement. 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?

What would be good botanicals to utilize in an aquarium representing this habitat?Well, some of our palm-derived selections would be a good start! Since palms are an important part of this habitat, it would only make sense that these materials form an important part of your aquascape, right?

Scattering these 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 of the above and just sort of "do it up" that way, so as to emphasize the abundance of several dominating plant species in the locale.

Although not as productive as the Amazon River itself, 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! 

There you have it... a brief summary of two completely different- even opposite- types of aquatic habitats- seldom replicated, yet perfect for aquarium representations! Both influenced significantly by underwater topography.

We have no shortage of wood and botanical materials to experiment with to replicate these environments in our aquariums. Redirecting flow, creating hiding places for fishes, and fostering epiphytic growth of biofilms and such are just a few of the obvious items to check off the "to-do" list when recreating the functional and aesthetic aspects of these unique niches.

This is fun! 

Dive deeper. Consider the "complete package" the next time you set up an aquarium- not just the look. You might just find that you're pushing the needle on the state of the art of the aquarium hobby just a bit farther, right?

I think so.

Stay thoughtful. Stay creative. Stay motivated. Stay resourceful. Stay diligent...

And Stay Wet.


Scott Fellman
Tannin Aquatics 

Scott Fellman
Scott Fellman


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