Working it... Nature's processes...

Part of the whole "game" of the botanical-style aquarium is understanding how, why and what happens to terrestrial materials when they're placed in water.

Nature has been working with terrestrial materials in aquatic habitats for eons.

And Nature works with just about everything you throw at her!

She'll take that seemingly "unsexy" piece of wood or rock or bunch of dried leaves, and, given the passage of time, the action of gravity and water movement, and the work of bacteria, fungi, and algae- will mold, shape, evolve them into unique and compelling pieces, as amazing as anything we could ever hope to do...

This is true in both the wild habitats and the aquarium, of course.

The same processes and function which govern what happens to these materials in the wild occur in our aquariums. And, if we reject our initial instinct to "edit" what Nature does, the aquarium takes on a look and vibrancy that only She can create.

We're hitting on this "what happens when.." theme again today, because we've seen more and more newcomers to our world aspiring to work with botanicals. Although at this point in 2020, the calendar matters a lot less than it did in previous years thanks to the pandemic, the approaching autumn seems to be that "trigger" which stimulates the creation of new aquariums. 

And new aquariums, combined with new botanical-style aquarium enthusiasts bring with them new expectations, new ideas, and new processes to understand.

Oh- mental shifts, of course! (You knew I'd say that.)

We also have to re-adjust our aesthetic preferences to accept the appearance of these processes. We need to understand why biofilms form, why terrestrial materials decompose underwater, and how this impacts-and benefits- the environment in our aquariums.

There is more to this than just crafting a "look and layout."

You don't have to start with a real high concept, in terms of laying out your botanicals and leaves. A lot of hobbyists ask me about the best way to place botanicals in their tanks, and the simple truth is that there IS no "best way."  You can place seed pods and leaves and such wherever you want to in the tank, but processes like water movement, decomposition, and the activities of our fishes will sort of "re-distribute" these materials.

Again exactly what happens in Nature. In an ironic twist on the traditional way of 'scaping and running aquariums, WE as hobbyists actually have to accept a certain amount of "editing" by Nature!

So, what exactly happens when terrestrial materials- like leaves, seed pods, and wood, are submerged in water?

Let's talk a cursory look at it!

Anyone who's ever cured a piece of wood, thrown in a bunch of seed pods, or laid down some leaves in their aquarium has seen the emergence of biofilms and fungal growth.

This much-maligned stuff is something those of us who play with leaves and botanicals know all too well. It's something we see in our aquariums, as well as in the wild aquatic habitats around the world.Biofilms form when bacteria adhere to surfaces in some form of watery environment and begin to excrete a slimy, gluelike substance, consisting of sugars and other substances, that can stick to all kinds of materials, such as- well- in our case, botanicals.


It starts with a few bacteria, taking advantage of the abundant and comfy surface area that leaves, seed pods, and even driftwood offer. The "early adapters" put out the "welcome mat" for other bacteria by providing more diverse adhesion sites, such as a matrix of sugars that holds the biofilm together.

Since some bacteria species are incapable of attaching to a surface on their own, they often anchor themselves to the matrix or directly to their friends who arrived at the party first.

 And we could go on and on all day telling you that this is a completely natural occurrence; bacteria and other microorganisms taking advantage of a perfect substrate upon which to grow and reproduce, just like in the wild. Freshly added botanicals offer a "mother load"of organic material for these biofilms to propagate, and that's occasionally what happens - just like in Nature.  

They are not only typically harmless in aquariums, they are utilized as a supplemental food source by a huge variety of fishes and shrimps in both nature and the aquarium. They are a rich source of sugars and other nutrients, and could prove to be an interesting addition to a "nursery tank" for raising fry if kept in control. Like, add a bunch of leaves and botanicals, let them do their thing, and allow your fry to graze on them!

And then, there are the fungi.

Fungi feed by absorbing nutrients from the organic material in which they live. Fungi do not have stomachs, and must digest their food before it can pass through the cell wall into structures called hyphae (the threads that form the body of a fungus- the part that you see all over that sexy piece of wood you just added your tank!). Hyphae secrete acids and enzymes that break the surrounding organic material down into simple molecules they can easily absorb.

Fungi have evolved to use a lot of different items for food. Some are decomposers living on dead organic material like leaves. these are the guys we typically encounter in our botanical-style aquariums' leaf litter/botanical beds!

Fungi reproduce by releasing tiny spores that then germinate on new and hospitable surfaces (ie, pretty much anywhere they damn well please!). These aquatic fungi are involved in the decay of wood and leafy material. And of course, when you submerge terrestrial materials in water, growths of fungi tend to arise.

Fungi tend to colonize wood because it offers 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?

And of course, many fishes and invertebrates which live amongst and feed directly upon the fungi and decomposing leaves and botanicals contribute to the breakdown of these materials as well! Aquatic fungi can break down the leaf matrix and make the energy available to feeding animals in these habitats.

And look at this little gem I found in my research:

"There is evidence that detritivores selectively feed on conditioned leaves, i.e. those previously colonized by fungi (Suberkropp, 1992; Graca, 1993). Fungi can alter the food quality and palatability of leaf detritus, aecting shredder growth rates. Animals that feed on a diet rich in fungi have higher growth rates and fecundity than those fed on poorly colonized leaves. Some shredders prefer to feed on leaves that are colonized by fungi, whereas others consume fungal mycelium selectively..."

"Conditioned" leaves, in this context, are those which have been previously colonized by fungi! They make the energy within the leaves and botanicals more available to higher organisms like fishes and invertebrates! 

After all of this, comes the break down- the decomposition- of the materials we add to our tanks.

If there is one aspect of our botanical-style aquariums which fascinates me, it's the way they facilitate the natural processes of life- specifically, decomposition.

We use this term a lot around here...What, precisely does it mean?

de·com·po·si·tion- dēˌkämpəˈziSH(ə)n -the process by which organic substances are broken down into simpler organic matter.

A very apt descriptor, if you ask me! 

We add leaves and botanicals to our aquariums, and over time, they start to soften, break up, and ultimately, decompose. This is a fundamental part of what makes our botanical-style aquariums work. Decomposition of leaves and botanicals not only imparts the substances contained within them (lignin, organic acids, and tannins, just to name a few) to the water- it serves to nourish bacteria, fungi, and other microorganisms and crustaceans, facilitating basic "food web" within the botanical-style aquarium- if we allow it to!

Decomposition of plant matter-leaves and botanicals- occurs in several stages.

It starts with leaching -soluble carbon compounds are liberated during this process. Another early process is physical breakup or fragmentation of the plant material into smaller pieces, which have greater surface area for colonization by microbes. 

Does the liberation of carbons, sugars, etc. in our systems impact the water quality of our aquariums? Of course it does! And you need to monitor water quality in your aquariums regularly, to establish what's "baseline" for your system.

It's important to remember that leaves and such are simply not permanent additions to our 'scapes, and if we wish to enjoy them in their more "intact" forms, we will need to replace them as they start to break down. 

This is not a bad thing.

Much like flowers in a garden, leaves will have a period of time where they are in all their glory, followed by the gradual, inevitable encroachment of biological decay.

At this phase, you may opt to leave them in the aquarium to enrich the environment further and offer a new aesthetic, or you can remove and replace them with fresh leaves and botanicals.

Again, this is very much replicates the process which occur in nature, doesn't it? Stuff either remains "in situ" as part of the local habitat, or is pushed downstream by wind, current, etc.

(If you haven't figured it out by now, pretty much everything we do in a botanical-style blackwater aquarium has a "natural analog" to it!)

For most of us- those of us who've made that mental shift- we let Nature dictate the evolution of our tanks. We understand that the processes of biofilm recruitment, fungal growth, and decomposition work on a timeline, and in a manner that is not entirely under our control.

Nature works it!

Understanding that decomposition is an amazing process by which Nature processes materials for use by the greater ecosystem is really important.

It's the first part of the recycling of nutrients that were used by the plant from which the botanical material came from. When a botanical item decays, it is broken down and converted into more simple organic forms, which become food for all kinds of organisms at the base of the ecosystem.

In aquatic ecosystems, much of the initial breakdown of botanical materials is conducted by detritivores- specifically, fishes, aquatic insects and invertebrates, which serve to begin the process by feeding upon the tissues of the seed pod or leaf, while other species utilize the "waste products" which are produced during this process for their nutrition.

In these habitats, such as streams and flooded forests, a variety of species work in tandem with each other, with various organisms carrying out different stages of the decomposition process.

And we can replicate part of this process in our aquariums. I'm very confident about that.

Nature works it.

Yet, we have to play with Her.

We just plug along, feeding our fishes, doing water exchanges, and growing plants. We tend to our aquascapes, and watch things grow. And, over time, even the most diligently-maintained aquariums tend to look significantly different than when they did when they were first assembled.

It's an inevitable result of the processes by which Nature utilizes botanical systems in our aquariums.

So, yeah- there IS a lot to consider when utilizing botanical materials in your aquarium. It's far, far beyond the idea of just "dumping and praying" that has been an unfortunate "model" for how to utilize them in our aquariums for many years. It's more than just aesthetics alone...the "functional aesthetic" mindset- accepting the look and the biological processes which occur when terrestrial materials are added  to our tanks is a fundamental shift in hobby thinking.

By studying the process of decomposition in Nature and in our aquariums, I believe that we are contributing to an exciting progression of the art and science of aquarium keeping!

Stay studious. Stay observant. Stay diligent. Stay creative...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




Scott Fellman
Scott Fellman


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