There is something fascinating and enticing to me about the idea of keeping an aquarium system "going" for very long periods of time, occasionally changing things up; leaving the "operating system" largely intact, while replacing the "soft" components over time.
Let's say that you're kind of over your Southeast Asian Cryptocoryne biotope, and ready to head West to South America.
So, rather than tearing up the entire tank, removing all of the plants, the hardscape, the leaves and botanicals, and the substrate, you opt to remove say, only the plants and the driftwood/rocks from the tank; exchange a good quantity of the water.
Woooah! Crazy! You fucking rebel...
I know. I know. This isn't exactly earth-shattering.
On the other hand, in the world of the botanical-style aquarium, the idea of leaving the substrate and leaf litter/botanical "bed" intact as you "remodel" 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. Fishes are able to find new food sources; new hiding places..new areas to spawn.
Similar to what should happen in our aquaria, right?
The longer these materials are present in the ecosystem, the more they are utilized along the food chain by various aquatic life forms.
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. I think that we should continuously add more materials into the aquarium to replace those which have broken down.
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 significantly influenced by the amount and composition of said material to "operate" successfully over time. As existing material break down, new ones are constantly being added back into the environment.
Yeah, there is a natural "prototype" for this process.
And, in the aquarium, we can embrace this and replicate it.
This is similar to the Japanese aquascaping practice of "sozo haishoku" espoused by the "Master" of this in aquariums, the late Takashi Amano. This is the processs of removing of as much old substrate material as possible along with the plants it contains in an aquarium, and replacing them with new materials.
It preserves the overall "composition" of the layout, but the "softscape" (botanicals and leaves, in our case) could change dramatically.
As we talked about many times before, removing old materials and replacing them with new stuff does sort of mimic what happens in many streams and rivers on a seasonal basis: Older materials are swept downstream as the watercourses swell, and are replaced by new ones that arrive to replace them.
And of course, in the aquarium, performing a "sozo haishoku"-type replacement of materials can significantly change the aesthetic of the aquascape because the botanicals are replaced with different ones after the previous ones are removed. In Nature, the underwater "topography" is significantly affected by these events, removing old feats and replacing them with new ones.
On the "downside", it can also create significantly different environmental parameters when we do big "change-ups" of materials in a short span of time; the impacts on our fishes may be positive or negative, depending upon the conditions which existed prior to the move.
Okay, I might just be torturing this simple idea to death- I admit this point that I'm probably not adding much more to the "recipe" here; likely simply being redundant and even a bit vague...However, I think we need to think about how interesting and indeed, transformative this simple practice is.
And yeah, I'll concede that we probably don't have every answer on the processes which govern this stuff.
The most common question I get when it comes to taking out a fair amount of this material and then "continuing" the tank is, "Will it cycle again?"
And the answer is...Sure, it could.
On the other hand, here is my personal experience:
Remember, I keep a sort of diary of most of my aquarium work. I have for over three decades (gulp...). Just random scanning my "diary", I see that I have executed this practice dozens of times in all types of aquariums, ranging from simple planted aquariums to hardscape-only tanks, to botanical-style, blackwater and brackish aquariums, to reef tanks.
Not once- as in never- have I personally experienced any increase in ammonia and nitrite, indicative of a new "cycle."
Now, this doesn't mean that I guarantee a perfect, "cycle-free" process for you. I'd be a complete asshole if I asserted that!
On the other hand, by leaving the bulk of the substrate material intact, and continuing to provide "fuel" for the extant biotia by leaving in and adding to the botanicals present in the aquarium, this makes a lot of sense.
I personally think our botanical-style systems, with their diverse and dynamic biology, rebound quickly. Much like the natural systems they purport to represent.
Sure, I have in place a mindset and husbandry practices that assure success with this idea.
Personally, I don't think that botanical-style aquarium are ever "finished." They simply continue to evolve over extended periods of time, just like the wild habitats that we attempt to replicate in our tanks do...
Stay engaged. Stay creative. Stay bold. Stay excited...
And Stay Wet.