The botanical-style aquarium is a little bit different than the typical approach to aquarium-keeping. Not only because they simply look different- but the fact that they rely on biological processes which we have often not given much thought to, other than a bit of apprehension over them.
Of all these processes, none is mentioned more frequently- or with as much reverence around these parts- as the process of decomposition. Yeah, you're actually hearing about a fish geek celebrating this- finding something compelling, fascinating, and fundamental about stuff breaking down in our tanks.
Decomposition, to refresh your memory, is the process by which organic materials are broken down into more simple organic matter. For our purposes, we are primarily interested in the breakdown of plant matter, ie; botanicals and leaves. It is in part responsible for some of the unique habitats that we love so much-and an inspiration for some unique aquariums with previously unappreciated aesthetics!
We can look at natural aquatic systems for inspiration and clues about how these systems are "powered" by an influx of botanical materials- specifically, leaves.
When leaves enter tropical streams and other bodies of water, fungal colonization increases the nitrogen content (because of fungal biomass) and causes leaf maceration. This is known by aquatic ecologists to be evidence of microbial colonization. There are many different stages in the process, starting with the leaching of materials from the cells of the botanicals during initial submersion, in which soluble carbon compounds are liberated in the process. A rapid release of phosphorus accompanies this leaching.
Of course, the process ultimately leads to physical breakdown and/or fragmentation of the leaves and botanicals into smaller "pieces", which possess larger amounts of surface area for microbial attachment. Extensive ecological studies done by scientists specifically in regard to leaf litter have yielded a lot of information about this process.
The fungi known as aquatic hyphomycetes produce enzymes which cause leaf maceration, and in as little as 2 to 3 weeks, as much as 15% of the decomposing leaf biomass in many aquatic habitats is processed by fungi, according to one study I found.
In experiments carried out by aquatic ecologists in tropical forests in Venezuela, decomposition rates were really fast, with 50% of leaf mass loss in streams occurring in less than 10 days!
The ultimate result is the transformation of what ecologists call "coarse particulate organic matter" (C.P.O.M.) into "fine particulate organic matter" (F.P.O.M.), which may constitute an important food source for other organisms we call “deposit feeders” (aquatic animals that feed on small pieces of organic matter that have drifted down through the water and settled on the substrate) and “filter feeders” (animals that feed by straining suspended organic matter and small food particles from water).
And yeah, insect larvae, fishes and shrimp help with this process by grazing among or feeding directly upon the decomposing botanical materials. So-called "shredder" invertebrates (shrimps, etc.) are also involved in the physical aspects of leaf litter breakdown.
So, there's a lot of supplemental food production that goes on in leaf litter beds and other aggregations of decomposing botanical materials. It's yet another reason why we feel that aquariums fostering significant beds of leaves and botanicals offer many advantages for the fishes which reside in them!
The biggest allies we have in the process of decomposition of our botanicals in the aquarium are microbes (bacteria, fungi, and protozoa, specifically). Ecologists will tell you that during the early decay phase of botanicals/leaves, the leaching of water-soluble substances plays a key role in the loss of the physical mass of these materials.
Alteration of the botanicals is done chemically via this microbial action; ultimately, the components within the botanicals/leaves (lignin, cellulose, etc.) are broken down near completely. In aquatic environments, photosynthetic production of oxygen ceases in submerged terrestrial plants and their parts, and organic matter and nutrients are released back into the aquatic environment.
Fungal colonization facilitates the access of invertebrates to the energy trapped in deciduous leaves and other botanical materials found in tropical streams. Bacteria and fungi that decompose decaying plant material in turn consume dissolved oxygen for respiration during the process.
This is why adding too much botanical material too rapidly to an aquarium can create big problems for the fishes! A rapid decrease in dissolved oxygen in a small body of water can be disastrous; or, at the very least, leave fishes gasping at the surface! And of course, that's why we tell you to deploy massive patience and to go slowly when adding botanicals to an established aquarium...
Now, I'm just one guy, but I personally haven't had issues with the complete decomposition of botanicals and leaves being left to accumulate in my aquariums. In almost three decades of playing with this stuff, and being a hardcore, water-quality-testing reef keeper during much of that time, I can't ever, EVER recall I time where the decline of a system I maintained could be pinned specifically on the detritus from decomposing botanical materials as a causative factor in reducing water quality.
In fact, I have never had a situation where water quality has been an issue in a tank not performing well. And I suspect- neither have many of you.
Okay, put me in for a medal, right?
That's not the point.
What I'm getting at is that I have always been a firm believer in some forms of nutrient export being employed in every single tank I maintain. Typically, it's regular water exchanges. Not "when I think about it', or "periodically", mind you.
Nope, it's weekly.
Now, I'm not saying that you can essentially disobey all the common sense husbandry practices we've come to know and love in the hobby (like not overcrowding/overfeeding, etc.) and just change the water weekly and everything's good.
Water exchanges are helpful. However, they're not a panacea for all of the potential "ills" of a poorly managed tank.
What I am saying is that incorporating regular water exchanges into your system gives you the ability to dilute any potential accumulating organics/pollutants before they become a significant negative ve impact on water quality.
They simply give you a bit of a "buffer", essentially.
I don't need to go into the well-trodden reasons about what water exchanges are a good thing in the aquarium. However, I do need to give us a collective whack upside the head and encourage each and every one of us to think about this stuff from the perspective of an overall closed ecosystem. Think about what the nitrogen cycle is and does, and think about the impact of inputs and exports into and out of our closed systems.
Pretty much everything we do in a botanical-style blackwater aquarium has a "natural analog" to it!
Some hobbyists have commented that, as their leaves and botanicals break down the scape as initially presented changes significantly over time. Wether they know it or not, they are grasping "Wabi-Sabi"...sort of.
("Again, Fellman?" Yes. This concept is really important!)
One must appreciate the beauty at various phases to really grasp the concept and appreciate it. To find little vignettes- little moments- of fleeting beauty that need not be permanent to enjoy.
And, despite their transience, these materials function as diverse harbors of life, ranging from fungal and biofilm mats, to algae, to micro crustaceans and even epiphytic plants. Decomposing leaves, seed pods, and tree branches make up the substrate for a complex web of life which helps the fishes that we're so fascinated by flourish.
And, if you look at them objectively and carefully, these assemblages-and the processes which form them- are beautiful- both in Nature and in the aquarium!
One need only study the wild aquatic systems of the world to realize that it's not all "crystal clear and sterile" out there- and that our aquariums in all of their tinted, murky glory, filled with fungal growth and decomposing materials- will reflect this.
Nature "calls the shots" here.
And that it's totally okay.
We are not managing botanical-style aquariums to be sterile glass boxes, "dioramas", or "zen gardens." It's not just a "look."
We are understanding that a real "nature/natural-style aquarium" embraces the processes of nutrient import/export, decomposition, bacteria/fungal growth, and long-term nutrient utilization by the organisms which we keep. The appearance is far different than a system strictly set up for aesthetics. Rather, our systems offer a unique combination of form AND function...what we call "functional aesthetics."
The "look" and the "function"- working hand in hand to create a replication of Nature far more authentic than what we've done in the past in the hobby. And what is required to execute this?
Patience. A long-term view. Observation. Understanding.
Embrace all of these things...and grow from the process.
Stay curious. Stay diligent. Stay involved. Stay brave...
And Stay Wet.