Disruption...Or simply Nature's process for change?

You often hear that old cliched expression, "If there is one thing that's constant, it's change..."

And it sort of applies to aquarium keeping...if we look to Nature.

When we look at the way natural aquatic habitats arise, evolve, and function, I can't help but thing about what factors force such processes.

A recent podcast with our friend, Tai Strietman, really brought this idea home. During our extensive discussion, Tai mentioned some of the observations he's made of natural habitats in The Pantanal region of Brazil, and the changes which impact the fishes which reside in them.

Tai explained that fishes are remarkably resilient, not only enduring- but exploiting- the seasonal changes and challenges their habitats face throughout the year. Everything from changing water depths, rising and dropping oxygen levels, to full-scale physical re-working of the underwater topography, to changing food resources.

It really got me thinking about parallels, similarities, and the very processes which create environmental changes which our fishes must adapt to in our aquaria. I think about two things: How strong and adaptable fishes are, and how intimately they are tied to their environment. Familiar themes that we've touched on a lot here, right?

In Nature, fishes will frequently migrate into and out of areas as the seasons change. Often, this is because they are following food sources, shelter, and stability. Instinctive urges to feed, reproduce, and flee predation compel fishes to move from environment to environment. 

I believe that our fishes can benefit from us offering some "disruption" or changes to the environment from time to time. I believe that many of them are genetically or instinctively "programmed" to endure- and even to benefit from -such environmental changes as part of their life cycles.

I realize that this is somewhat contrarian to the long-accepted aquarium standard of stability in every way, and it's something I've had to re-visit myself over the years...I mean, I've traditionally been the type of aquarist who adopts a sort of "hands-off" stance when it comes to "messing" with my tanks once they're up and running. However, when we consider the way Nature functions when She impacts aquatic ecosystems, there is something there, I think. In the wild, many fishes are subjected to such environmental fluctuations and disruptions to their physical environment on an almost semi-regular basis.  

They seem to do just fine.

In fact, we've embraced some aspects of this type of environmental manipulation with fish breeding technique for many years: Lowering water temperatures to mimic rainstorms for Corydoras, or exhaling into a test tube of water containing annual killifish eggs to add CO2 to the water to stimulate hatching, etc. 


I would imagine that there are a lot of benefits to be realized by "deconstructing" and replicating the processes of disruption and change which Nature imparts to our fishes environments.  We could gain a lot from simply studying and considering how fishes react to the environmental disruptions and changes that they face.

Think about the way fishes adapt their behaviors and strategies to feed in the wild...It might give us some interesting insights that we can apply to aquarium work.

As we all know, in Nature, fishes spend a significant amount of time and energy searching for food.

On the Amazonian floodplains, for example, the flood cycle of the rivers into the igapo are the dominant seasonal factor, and fish communities are found to fluctuate greatly over the year. During inundation, fish migrate into floodplain forests to feed on insects, fruits and seeds, among other things.

Studies of blackwater communities showed that, during these cycles, a greater diversity of fishes exists there. Many species were found to be specialized feeders. Fish, detritus and insects were the most important food resources supporting the fish community in both high and low water seasons, but the proportions of fruits, invertebrates and fish were reduced during the low water season.

Are there some "takeaways" here for us fish geeks?

Sure, I think so! 

Hmm, what this means to us is that fish sort of "follow the food", right? And that the "seasonal availability" of some food sources actually dictates overall fish behavior, and for that matter, which species are found in the habitats at various times of the year, and of course, what is consumed.

How would we replicate this seasonal change of food abundance and dietary composition in our aquariums? 

Perhaps we could simply alter the stuff we feed our fishes at different times of the year! In other words, feed a correspondingly more frequent, more intensive diet of say, worms, fruit flies, or Daphnia in a period of time that corresponds with the wet season?

And then, perhaps reducing frequency, quantity, and variety of foods at other times- perhaps even doing a several week-long "hiatus" or two, to encourage them to forage on the biocover and natural foods you have encouraged to accumulate within the aquarium?

That's one change that we could relatively easily recreate in the aquarium. I've done this a number of times over the years with tremendous success. It all revolves around how we set up our systems for this sort of operation.

Other changes or, if you will- disruptions, which we could replicate in our closed systems would be physically re-arranging or evolving the type and compositions of the materials in our tanks, or adding additional botanical materials (leaves and seed pods and the like) on top of existing materials.

This could realistically replicate the physical changes which happen to natural habitats when water levels ebb and flow and new materials are imported as others are pushed out.

Fishes will take advantage of all of these sorts of changes.

They'll "claim" new territories, while simultaneously exploiting new food resources as they become available. As Tai pointed out, when changes happen to the physical environments in which fishes reside, established social hierarchies will be disrupted and changed up. Not only will existing inter-specific social structures change- the very composition of the fish population itself will often change as newer, specialized feeders move in to take advantage of conditions favorable to their existence.

You can and should keep botanicals and leaves in the aquarium until they completely decompose. Why? What advantage is there to doing this in our aquariums?

In the aquarium, much like in the natural habitat, the layer of decomposing leaves and botanical matter, colonized by so many organisms, ranging from bacteria to macro invertebrates and insects, is a prime spot for fishes! The most common fishes associated with leaf litter in the wild are species of characins, catfishes and electric knife fishes, followed by our buddies the Cichlids (particularly Apistogramma, Crenicichla, and Mesonauta species)!

Some species of RIvulus killies are also commonly associated with leaf litter zones, even though they are primarily top-dwelling fishes.  Leaf litter beds are so important for fishes, as they become a refuge for fish providing shelter and food from associated invertebrates.

How often do you need to replace your leaves? Well, another great question for  which there is no "rule" involved. The reality is that you can simply add new leaves on a regular basis, so you'll always be making up for the ones that have decomposed. Some hobbyists like to remove the decomposed leaves, preferring a more "pristine" look.

It boils down to aesthetic preferences, really. There is nothing wrong with leaving them in until they completely break down. And you can add to them...build upon the layers that are already there. Just like what happens in Nature.

Of course, besides leaves and seed pods, there is that other "stuff" that we all love..Branches, stems...twigs.

Those of us who obsessively study images of the wild tropical habitats we love so much can't help but note that many of the bodies of water which we model our aquariums after are replete with tree branches and stems. Since many of these habitats are ephemeral in nature, they are only filled up with water part of the year.

The remainder of the time, they're essentially dry forest floors.

And what accumulates on dry forest floors?

Branches, stems, and other materials from trees and shrubs!

When the waters return, these formerly terrestrial materials become an integral part of the (now) aquatic environment. This is a really, really important thing to think of when we aquascape or contemplate how we will use botanical materials like the aforementioned stems and branches. They impact both function and aesthetics of an aquarium...Yes, what we call "functional aesthetics" rears its head again!

There is no real rhyme or reason as to how these materials orient themselves the way they do. I mean, branches fall off the trees, a process initiated by either rain or wind, and just land "wherever." Which means that we as hobbyists would be perfectly okay just sort of tossing materials in and walking away! Now, I know this is actually aquascaping heresy- Not one serious 'scaper would ever do that...right?

I'm not so sure why they wouldn't. 

I mean, what's wrong with sort of randomly scattering stems, twigs, and branches in your aquascape? It's a near-perfect replication of what happens in Nature. Now, I realize that a glass or acrylic box of water is NOT Nature, and there are things like "scale" and "ratio" and all of that "gobbldeygook" that hardcore 'scaping snobs will hit you over the head with...

But Nature doesn't give a fuck about some competition aquascaper's "rules"- and Nature is pretty damn inspiring, right? There is a beauty in the brutal reality of randomness. I mean, sure, the position of stones in an "Iwagumi" is beautiful...but it's hardly what I'd describe as "natural."

Nature is...well...

Which begs the question: Who really cares? Do what you like! However, I think that we could do a lot worse than literally dropping materials into our tanks (taking into account their size of course). 

Look to Nature. And be bold.

And other processes and actions we can take in our aquariums replicate the rather disruptive processes which occur in Nature- bringing many of the same challenges- and benefits-to the organisms which reside in them.

For example- when we make changes to our aquariums.

in the world of the botanical-style aquarium, the idea of leaving the substrate and leaf litter/botanical "bed" intact as you "remodel" the aquarium isn't exactly a crazy one. And conceptually, it's sort of replicates what occurs in Nature, doesn't it?

Yeah, think about this for just a second.

As we almost constantly discuss, habitats like flooded forests, meadows, vernal pools, igarape, and swollen streams tend to encompass terrestrial habitats, or go through phases where they are terrestrial habitats for a good part of the year.

In these wild habitats, the leaves, branches, soils, and other botanical materials remain in place, or are added to by dynamic, seasonal processes. For the most part, the soil, branches, and a fair amount of the more "durable" seed pods and such remain present during both phases.

The formerly terrestrial physical 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 complex, protected 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. Detritus settles.

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.  New populations of fishes are able to find new food sources, new hiding places, and new areas to spawn.

Life flourishes.


When you remove much of the hardscape, plants, etc. from the aquarium as you "evolve" it to something else, yet leave the substrate, some of the hardscape, leaves, etc. intact, you're essentially mimicking this process in a most realistic way.

Sure, a "makeover" of an aquarium can be a seriously disruptive event. On the other hand, if you take the mindset that this is a "transformation" of sorts, and act accordingly, it becomes more of an evolutionary process. It need not be viewed as some sort of huge, catastrophic process in the lifetime of the aquarium.

This is something I've done for many years- like a lot of you have, and it not only makes your life a bit easier- it can create pretty good outcomes for the fishes we keep.

No one said the hobby is easy, but it’s not difficult, either- as long as you have a basic understanding of the environmental processes and conditions within your aquarium. And the idea of leaving essential biological components of your aquarium more-or-less "intact" for an indefinite period of time is really compelling.

Of course, an aquarium which utilizes botanicals as a good part of its hardscape follows a set of phases, too. And I've found that once a botanical-style aquarium (blackwater or brackish) hits that sort of "stable mode", it's just that- stable. You won't see wildly fluctuating pH leaves, nitrates, phosphates, etc. To a certain degree, the aquarium has achieved some sort of "biological equilibrium."

Now, one thing that's unique about the botanical-style approach is that we tend to accept the idea of decomposing materials accumulating in our systems. We understand that they act, to a certain extent, as "fuel" for the micro and macrofauna which reside in the aquarium. The idea of leaving this material in place over the long-term is a crucial component of this approach, IMHO.

As we've discussed repeatedly, just like in Nature, they'll also form the basis of a  complex "food chain", which includes bacterial biofilms, fungi, and minute crustaceans. Each one of these life forms supporting, to some extent, those above...including our fishes.

I have long believed that if you decide to let the botanicals remain in your aquarium to break down and decompose completely, you shouldn't change course by suddenly removing the material all at once...Particularly if you're going to a new version of an existing aquarium.


Well, I think my theory is steeped in the mindset that you've created a little ecosystem, and if you start removing a significant source of someone's food (or for that matter, their home!), there is bound to be a net loss of biota...and this could lead to a disruption of the very biological processes that we aim to foster.

Okay, it's a theory...But I think I might be on to something, maybe? So, like here is my "theory" in more detail:

Simply look at the botanical-style aquarium (like any aquarium, of course) as a little "microcosm", with processes and life forms dependent upon each other for food, shelter, and other aspects of their existence. And, I really believe that the environment of this type of aquarium, because it relies on botanical materials (leaves, seed pods, etc.), is more signficantly influenced by the amount and composition of said material to "operate" successfully over time.

Just like in natural aquatic ecosystems...

The processes of change and disruption which occur in natural aquatic habitats- and in our aquariums- are important on many levels. They encourage ecological diversity, create new niches, and revitalize the biome. Changes can be viewed as frightening, damaging events...Or, we can consider them necessary processes which contribute to the very survival of aquatic ecosystems.

Think about that the next time you hesitate to remove or replace that piece of driftwood, or toss some fresh leaves on top of your existing bed of botanicals, or...

Stay thoughtful. Stay bold. Stay creative. Stay studious...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


3 Responses

Joshua E Morgan
Joshua E Morgan

October 14, 2020

I have several high tech tanks at the moment…plants do indeed consume CO2, but in practice the amount of CO2 a tank has when being supplied with the gas has more to do with the amount of gas exchange at the surface than with the plants. I was going to experiment with this idea at least a few weeks before I got any fish in the tank to make sure it works properly…fish CO2 tolerances vary, but very few (if any) freshwater fish would take issue with the 10-15 ppm CO2 I was going to use in the soft water tank (common high tech levels are 20-30 ppm). Thanks for your thoughts, by the way :)

Scott Fellman
Scott Fellman

October 14, 2020

Hi Joshua,

Interesting thoughts. I don’t see why you couldn’t apply CO2. However, you’d have to be quite careful, in the absence of plants which consume it, not to drive down the oxygen levels in the tank to the point where you’d literally be suffocating your fishes, right? I mean, I may be being a bit over dramatic, but I would assume that excess of CO2 could lead to issues if you’re not careful. And I wonder about how much and how long ( or if it would be continuous) you’d need to do this in order to drive down the pH to the levels you want. The longer term implications of health issues and other potential problems concern me. However, I admit that I’m not well-versed on using CO2 for anything but calcium reactors and, to a lesser extent, aquatic plants, so it may be worth you researching more. Most hobbyists who play with really trying to hit lower pH seem to play with various acid solutions and such, as opposed to CO2 (in fact, your question is the first time I have personally heard of the idea!)…Bottom line: Do some more research with hobbyists better versed at playing with this stuff than I, and let us all know what you find! 😆. Good luck



October 13, 2020

Cool :) I have long been considering culturing Moina sp outside during the summer to feed my fish, and this may be a catalyst to me actually trying to do so. So we should just leave the botanicals until they decay entirely into unrecognizable detritus? Also, here’s an (unrelated) idea I was looking for thoughts on…could I use CO2 injection (at about 10-15 ppm) to reduce the PH in a soft water tank without influencing the TDS very much? This would most likely for a fanatical soft water fish like licorice gouramies, which have been known to thrive and breed in a PH as low as the high 2’s (not that I am going to keep the PH of the tank quite that low…more likely the 4’s, at lowest 3’s)

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