The contrarian embrace of decomposing stuff in our tanks..

The world of botanical style aquariums is exploding.

Someone asked me recently about how I feel about having botanicals completely beak down in my aquarium. As in, just leaving them in until they're essentially inert.

My responses it has been for years, is that I'm perfectly fine with just leaving them in! The reality, as I see it, is that there is simply nothing wrong with this. I know, I know-it sort of goes against many years of aquarium hobby doctrine, which suggests that it's a bad idea to allow materials to decompose in your tank.

Now, of course, this is not bad advice, in general. We've been admonished to remove stuff like uneaten food,  fish poop, dead plant leaves, deceased fishes, etc. from our tanks. The rationale, for years, has been that the breakdown of organic materials can lower the pH of the aquarium water by releasing carbon dioxide, which is converted to carbonic acid in water. This carbonic acid, in turn, can rapidly drop the pH, and...


Of course, in addition to the potential to drop the pH of your tank quickly, the decomposition of stuff like uneaten food has historically been implicated in the clogging of filter media, reducing flow through the aquarium, which, in theory,  may result in a lower dissolved oxygen content, a drop in pH, a rise in ammonia and nitrite know, the usual bad stuff.

So, is there any difference between uneaten fish food and allowing your botanical materials to break down fully in situ? 

Well, not necessarily. The process is the process, right?


Of course, fish foods are high in compounds like phosphate, which can lead to excessive algae growth if left unchecked. So, yeah, you HAVE to embrace basic husbandry (like water exchanges, good filtration, etc.) in your aquarium work. This is nothing new. Don't overfeed, and don't let vast amounts of uneaten food accumulate in your tank. Do regular water exchanges. "Aquarium Keeping 101."

However, the difference is that we, as lovers of natural, botanical-style aquariums are more thoughtful and deliberate about fostering that ol' microbiome- the vast community of organisms which reside our tanks and process the available nutrients. We don't spend our days fanatically "editing" Nature's real "cleanup crew" of fungal growths, bacterial biofilms, etc. 

By actually embracing these organisms and encouraging them to grow and reproduce in our tanks, we're creating a vast nutrient export capability...One which utilizes materials like botanicals and leaves for "fuel", liberating nutrients and serving, on occasion, as a supplemental food source- part of the "food web"-in our aquariums.


I think that what's different is that we are now accepting the use of these materials for a combination of reasons- what we call "functional aesthetics"- the ability of a material to influence the look and the function of the aquarium environment simultaneously.

A real "mental shift..."

And of course, there are aesthetic components to this...

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. 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 impermanence, 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 are beautiful.

This is not something "new" or previously unconsidered by the hobby, but it's something we don't give much thought to, I think. Of course, when we look at natural ecosystems where leaves and other botanical materials collect, the parallels in look and function become far more obvious!

Understanding the transient nature of botanical materials is absolutely essential for the botanical-style aquarium enthusiast. There are many who prefer a crisp, clean collection of botanicals and leaves in their tanks, and go to great effort to keep them that way...They will remove any leaf that starts to break down or recruit biofilms, and replace them with new ones. Cool, I suppose, but it's sort of the "aesthetics over function" mindset that currently dominates aquarium keeping...It also denies these organisms the ability to process these materials, right?

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. We leave these materials in, and embrace Nature's work.

Decomposition is an amazing function, in which Nature process materials for use by the greater ecosystem. 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 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.

Some organisms, such as nematodes and chironomids ("Bloodworms!") will dig into the leaf structures and feed on the tissues themselves, as well as the fungi and bacteria found in and among them. These organisms, in turn, become part of the diet for many fishes.

And the resulting detritus produced by the "processed" and decomposing pant matter is considered by many aquatic ecologists to be an extremely significant food source for many fishes, especially in areas such as Amazonia and Southeast Asia, where the detritus is considered an essential factor in the food webs of these habitats.

And of course, if you observe the behavior of many of your fishes in the aquarium, such as characins, cyprinids, Loricarids, and others, you'll see that in between feedings, they'll spend an awful lot of time picking at "stuff" on the bottom of the tank. In a botanical style aquarium, this is a pretty common occurrence, and I believe an important benefit of this type of system. 

I am of the opinion that a botanical-style aquarium, complete with its decomposing leaves and seed pods, can serve as a sort of "buffet" for many fishes- even those who's primary food sources are known to be things like insects and worms and such. Detritus and the organisms within it can provide an excellent supplemental food source for our fishes!

Just like in Nature. 

That being said, I think we need to let ourselves embrace this stuff and celebrate it for what it is: Life. Sustenance. Diversity. Foraging. I think that those of us who maintain botanical-style aquariums who have made the "mental shift" to understand, accept, and even appreciate the appearance of this stuff, just look at things differently.

Natural habitats are absolutely filled with this every nook and cranny. It's like the whole game here- an explosion of life-giving materials, free for the taking...

It's not everyone's idea of beauty. It requires us to let go...embrace something that seems so contrarian...yet is so elegant, beneficial, and remarkably reliable.

A true gift from Nature. 

Yet, for a century or so in the hobby, our first instinct is to reach for the algae scraper or siphon hose, and lament our misfortune with our friends.

It need not be this way. Its appearance in our tanks is a blessing. 

A truly "natural" aquarium is not sterile. It encourages the accumulation of organic materials and other nutrients- not in excess, of course. Biofilms, fungi, algae...detritus...all have their place in the aquarium. Not as an excuse for lousy or lazy husbandry- no- but as a means to process nutrients, and to provide supplemental food sources to power the life in our tanks.


Maybe not.

Stay curious. Stay thoughtful. Stay bold. Stay observant. Stay consistent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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