Of almost all of the natural processes that we in the botanical-style aquarium movement embrace, the process of decomposition is pretty much the "foundational" one that impacts our systems.
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!
When leaves enter tropical streams and other bodies of water, fungal colonization causes leaves to increase the nitrogen content of the water (because of fungal biomass), and the process of leaf maceration begins. This is considered 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 also 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.
Fungi tend to colonize wood and botanical materials, because they offer them a lot of surface area to thrive and live out their life cycle. And cellulose, hemicellulose, and lignin- the major components of wood and botanical materials- are degraded by fungi which posses enzymes that can digest these materials! Fungi are regarded by biologists to be the dominant organisms associated with decaying leaves in streams, so this gives you some idea as to why we see them in our aquariums, right?
In aquairum work, we see fungal colonization on wood and leaves all the time. Most hobbyists will look on in sheer horror if they saw this extensive amount of fungal growth on their carefully selected, artistically arranged wood pieces! Yet, it's one of the most common, elegant, and beneficial processes that occurs in Nature!
Of course, fungal colonization of wood and botanicals is but one stage of a long process, which occurs in Nature and our aquariums. Of course, as hobbyists, once we see those first signs of this stuff, the majority of us tend to reach for the algae scraper or brush and remove as much of it as possible- immediately! And of course, this provides some "aesthetic relief" for some period of time- but it comes right back...because these materials will provide a continuous source of food and colonization sites for fungal growths!
And the idea of "circumventing" this stuff is appealing to many, but the reality is that you're actually interrupting the process. Nature abhors a vacuum, and new growths will return to fill the void, thus prolonging the process.
Although decomposition is a continuous process, taking place over long periods of time, studies carried out by aquatic ecologists in tropical forests in Venezuela demonstrated that 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...We've talked about that quite recently, right? So-called "shredder" invertebrates (shrimps, etc.) are also involved in the physical aspects of leaf litter breakdown.
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!
I have personally experienced this time and time again, by setting up botanical-style systems for the expressed purpose of providing supplemental food for the resident fishes. I've done this with adult fishes, and I've actually "reared" (well, Nature dod the work) many fish fry to maturity by setting them up in heavy botanical-stocked systems with little to no supplemental feeding. The fishes feed on the fungal growths and biofilms, as well as the organisms which are associated with them...just like in Nature.
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 of the botanicals/leaves (lignin, cellulose, etc.) are broken down near completely. In aquatic environments, photosynthetic production of oxygen ceases in plants, and organic matter and nutrients are released back into the aquatic environment.
All of these organisms work together- in essence, supporting each other via the processes which they engage in.
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.
Of course, if you intervene by removing stuff- or, more commonly- by adding too much stuff in too short a period of time- bad things can happen.
This is why adding too much botanical material too rapidly to an aquarium can create 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...
And, as we discussed yesterday, the processes of decomposition and utilization of dissolved organic carbon from botnanical materials keep the water quality high, even in a closed aquarium with a ton of botanical materials breaking down!
It's thought by ecologists that the dissolved organic carbon is used as a "substrate" for microbial growth- thusly lowering the concentration of dissolved organic carbon in the water, and transferring energy from decomposing leaves and other materials to other trophic levels (defined as "hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.").
Now, I've played with the idea of "curing" wood directly in the aquarium, as opposed to doing it in a separate container many times, too. Now, I can't say that this would be everyone's cup of tea, as it creates a very "disturbing" look for many hobbyists! Aesthetics aside, I personally don't see a problem with breaking in a new, fishless aquarium by "curing" the wood and such
You just need to be super patient. You need to wait until the fugal growths peak and subside substantially. You need to keep your hands off and just...wait. So what advantage would such a practice bring? For one thing, you'd have a well-established cycle of microbial colonization, biological succession, breakdown and ultimately, decomposition before fishes are ever present.
You just have to look at the process as the beginning of a long, continuous journey, one that can take your aquarium to all sorts of amazing places if you[re incredibly patient, diligent, make the effort to understand what's happening.
Faith in Nature.
It's all about how the natural materials that we play with fuel the process of establishing, growing, and maintaining a closed ecosystem in our aquaria. Knowing that the turbid, biofilm-and-fungal-growth-filled aquarium that you've recently set up will evolve over time to a rich, diverse, biologically stable microcosm.
I think it's a sort of exciting frontier. The idea of "throwing it all together" and letting Nature sort it out isn't laziness. It isn't some crazy, alternative approach, either. It's a slightly different take on what hobbyists have been doing for generations. The reality is that it's simply a way to create a very dynamic ecosystem by powering up things immediately. Taking a longer, less aesthetically conventional road. An approach that can unlock so many secrets of Nature to so many hobbyists.
And it's really as much of a mental shift as it is anything else- like so much of what we do with botanical-style aquarium systems. The willingness of us to really look to Nature as more than just an inspiration for making cool-looking aquariums. Rather, an approach which understands that our botanical-style aquariums require us to step back and observe what happens in wild aquatic habitats, and realizing that the same processes occur in our aquariums.
An understanding that "intervening" and "editing" the process by removing "undesirable" life forms is actually interfering with the development of a dynamic ecosystem.
Please consider such an approach. Please consider embracing the process of letting Nature do what she does, with the organisms which have evolved over eons to take advantage of the resources available to them. Understand how botanicals and wood "fuel" the process.
Stay diligent. Stay patient. Sty observant. Stay engaged...
And Stay Wet.