A growing, breathing...evolving microcosm...

As more and more hobbyists play with the "botanical/blackwater"-style aquarium concept, we're seeing more experimentation, more new ideas, and a lot of interest related to the setup, husbandry, and long-term operation of these systems. We talk a lot here about the fact that a botanical-style aquarium is sort of always "evolving", as we are continuously adding, removing, or rotating in new botanicals and leaves to replace those which have decomposed. It's a bit different than a typical aquarium  because you're sort of "editing on the fly" on a more or less continuous basis.  This dovetails nicely with the "maturing process" of an aquarium- specifically, thoughts on what the difference is between a tank that is just “cycled”, and one that is defined as “mature.” 

I guess the logical place to start such a discussion would be…at the beginning. Well, the beginning phases of your tank, that is.  You know what I mean: You’ve designed the perfect  system. You have a beautiful, low-iron glass aquarium, the best filter you can afford, an insanely tuned LED lighting system...You're going to represent an asian-themed blackwater habitat, and your fish choices are looking good. You've selected some choice leaves and botanicals from an online vendor (hmm, who could that be...?) and you're ready to go. Yeah, this tank is gonna rock!

Of course, before all of the fish are swimming about peacefully in their new home, you need to “cycle” the system, and get it suitable for life forms to reside in. It’s one thing to have a nicely-equipped system, quite another to have a suitable system for life. It’s still another when it earns the lofty hobby moniker of “mature.” 

I am operating on the assumption (gulp) that most of us have a  basic understanding of the nitrogen cycle and how it impacts our aquariums. However, maybe we don’t all have that understanding. My ramblings have been labeled as “moronic” by at least one “critic” before, however,  so it’s no biggie for me as said “moron” to give a very over-simplified review of the “cycling” process in an aquarium, so let’s touch on that for a moment! 

During the cycling process, ammonia levels will build and then suddenly decline as the nitrite-forming bacteria multiply in the system. Because nitrate-forming bacteria don't appear until nitrite is available in sufficient quantities to sustain them, nitrite levels climb dramatically as the ammonia is converted, and keep rising as the constantly-available ammonia is converted to nitrite. Once the nitrate-forming bacteria multiply in sufficient numbers, nitrite levels decrease dramatically, nitrate levels rise, and the tank is considered “fully cycled.”

So, in summary, you could correctly label your system “fully cycled” as soon as nitrates are detectible, and when ammonia and nitrite levels are undetectable. This usually takes anywhere from 10 days to as many as 4-6 weeks, depending on a number of factors. In my experience, there are certainly some “cheats” you can use to speed up the process, such as the addition of some filter media or sand from a healthy, “mature” aquarium, or even utilizing one of the many commercially available “bacteria in a bottle” products to help build populations of beneficial bacterial populations. I hate cheating...but I kind of like some shortcuts on occasion!

So we have at least, for purposes of this discussion, established what we mean in aquarium vernacular by the term “fully cycled.” However, what does “mature” mean? Well, here is where we lose some of the hard facts and get into judgment calls and opinion…and that’s okay. I’ll give you my thoughts on the topic, and I expect to hear yours!

In my opinion, a “mature” aquarium is a system in which the nitrogen cycle is fully functioning, and nitrate is regularly produced as the “end product” of the biological filtration process. However, it goes further than that. I believe that truly “mature” systems have several distinct traits that set them apart from newly-cycled systems, specifically:

*Significant populations of microfauna, algae, and even plants are in the system, with very few anomalous “crashes” or fish deaths occurring. Ammonia and nitrite are undetectable in the aquarium. Stability exists in terms of animal populations and environmental fluctuations.

*Microalgae is present in manageable quantities along with other macro life. Substrate is clean and not excessively filled with detritus. Botanical materials are softening and decomposing without a measurable impact on water quality (i.e.; your beneficial bacteria can "handle" any decomposition of botanicals without significant impact on water quality).

*Fish population has been stable, healthy and consistent, with few losses of any frequency.

*Plants, if present, are actively growing and increasing in size as well as improving in health and color. 

What’s more, there is a certain “Something” to a mature aquarium…A smell, a look, a lack of excess in either “good” or “bad” animals.  Hardly scientific, I know- but true, right? In my opinion, a “mature” tank is one in which you don’t have to freak out every time you miss a water change, forget to feed, fall behind on algae scraping, top-offs, etc. Aquariums that are environmentally stable allow the aquarist a certain degree of latitude in maintenance and overall husbandry. But that doesn’t mean you can kick back, of course.

With a botanical-style aquarium, you're typically adding and removing leaves and pods and such regularly; I pretty much do this during every water exchange. In addition to the obvious aesthetic "refresh", you get a new bump of humic substances and tannins from the freshly-prepared botanicals you're adding. And of course, adding anything to your aquarium that breaks down is "bioload", and you need to continuously observe your aquarium and test the water regularly to detect and follow any "trends" in the chemistry that could prove to be a source of concern.

Mature tanks also can fall into what author/reef great/friend Mike Paletta referred to as “Old Tank Syndrome” back in 2006 in a reef aquarium publication (although this is perfectly adaptable concept to freshwater aquariums, too). Mike asserts (correctly, IMHO) that an aquarium, no matter how biologically diverse or successful, simply is NOT a  true “slice of the bottom”; rather, that it is a closed system, and is potentially subject to accumulations of nutrients (specifically nitrogenous waste and phosphates) over time, some of which can reach a detrimental concentration unless regular maintenance is conducted to combat their accumulation.

Regular, though not obsessive- water parameter monitoring is also always advisable to ascertain just what is going on in the aquarium. The need to monitor  parameters like ammonia, nitrite, and nitrate is obvious, but you also need to look at pH. When you're dealing with a lower ph, low carbonate hardness system, TDS may ultimately prove a more useful "yardstick" than pH in the long run, but for many of us, a good pH meter can provide an accurate assessment of the pH of the system regularly. We’ve talked previously about establishing “baseline” operating parameters for your tank, and trying to stay within that baseline for the life of the aquarium.

In other words, even with regular maintenance practices and monitoring in place, you can’t truly set the tank “on autopilot” and let it run itself. There is a constant “war” between good and bad chemical concentrations going on in your system, and you need to be on top of things in order to assure that the “bad” doesn’t outweigh the “good.” 

Nothing really new here, except to say that with intentionally decomposing botanicals in the aquarium, the need to be on top of things is simply a more obvious priority. This type of aquarium is truly a constantly evolving microcosm, very similar in many respect to a natural stream or river. 

How do you know that you have excesses of organic nutrients building up in your long-established tank? Well, when you start noticing outbreaks of algae where none existed previously, that’s one tip off- as is the failure of previously thriving fishes to display the growth and vigor they once did. There are other signs, many of which an experienced fish keeper just sort of "knows."  As is often asserted, an aquarium is a lot like a terrestrial garden in many respects, and you’ll need to “prune” it regularly.

In our botanical aquarium example, the "pruning" is metaphorical, and represents the act of periodically removing and replacing decomposing leaves and other materials to keep  the parameters from "falling out of line." However, I can state categorically that in the 7 or so years since I've started playing with botanicals in my aquariums, I have not had this happen. Common sense husbandry, attention to what's happening in the aquarium, and learning what's "baseline" for the system have always given me stable, low-nutrient systems.

I have long theorized (completely anecdotally, of course) that the botanicals in our systems offer a significant "media" for beneficial microorganisms to thrive among, which serve to break down organics very effectively. Sort of the way a "deep sand bed" functions in a reef tank. Maybe even some denitrification occurring, in addition to fungal and microbial growth?

An interesting idea that is worth more serious research, IMHO!

The bottom line is that a botanical-style aquarium, being a closed system like any other, will demonstrate some characteristics that are easily identifiable when it’s “mature”, yet you still need to address consistency through aspects of husbandry and maintenance throughout its existence. Much like a garden, an aquarium could “run wild” if left to its own devices, and the outcome for many fishes and plants in residence could be negative- or at least, significantly different than what you intended to create!

No one said that working with specialty aquariums is super easy, but it’s not difficult, either- as long as you have a basic understanding of the environmental processes and conditions within your aquarium. 

So much to learn here, isn't there? 

Stay vigilant. Stay observant. Stay relentless.


And Stay wet.

Scott Fellman

Tannin Aquatics


Scott Fellman
Scott Fellman


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