"Research and Development..."

One of the most exciting things about botanical-style/blackwater aquariums is that there is so much that we still don't know. Despite an explosion of interest in this unique approach to natural aquariums, there's still a significant amount of unknowns.

Hobbyists have been adding botanical materials, in the form of wood, twigs, and leaves, for generations. Yet the rationale behind there use for many years was to provide a natural form of "decor", as opposed to looking at things from the standpoint of aesthetics and function.

With benefits of the use of these materials becoming more apparent to all who play with them in their aquariums, we're starting to see a shift towards trying to understand just what it is about these materials that is so beneficial to our fishes!

And of course, the key to understanding the "how's and why's" of botanical-style aquariums starts with understanding the role that these materials play in natural aquatic habitats.

There's been a fair amount of research and speculation by both scientists and hobbyists about the processes which occur when terrestrial materials like leaves and botanical items enter aquatic environments, and most of it is based upon field observations.

As hobbyists, we have a rather unique opportunity to observe firsthand the impact and affects of this material in our own aquariums! I love this aspect of our "practice", as it creates really interesting possibilities to embrace and create more naturally-functioning systems, while possibly even "validating" the field work done by scientists!

It goes without saying that there are implications for both the biology and chemistry of the aquatic habitats when leaves and other botanical materials enter them. Many of these are things that we as hobbyists also observe every day in our aquariums! We see firsthand how leaves and botanical materials impact the life of our fishes and other aquatic organisms in these closed systems.

"Indoor fieldwork", if you will!

That's what we do...

Phenomenon such as the appearance of  our friends, the biofilms- long a topic that simply never came up in the hobby outside of dedicated shrimp keepers- are now simply "part of the equation" in a properly-established botanical-style aquarium. We understand that they appear as a normal part of the process when terrestrial materials become submerged under water. We're seeing them for the benefits they provide for our systems, rather than freaking out and panicking at their first appearance!

This is a fairly profound shift in the hobby, if you ask me!

A lab study I came upon found out that, when leaves are saturated in water, biofilm is at its peak when other nutrients (i.e.; nitrate, phosphate, etc.) tested at their lowest limits. This is interesting to me, because it seems that, in our botanical-style, blackwater aquariums, biofilms tend to occur early on, when one would assume that these compounds are at their highest concentrations, right? And biofilms are essentially the byproduct of bacterial colonization, meaning that there must be a lot of "food" for the bacteria at some point if there is a lot of biofilm, right?

More questions...

Does this imply that the biofilms arrive on the scene and peak out really quickly; an indication that there is actually less nutrient in the water? Is the nutrient bound up in the biofilms themselves? And when our fishes and other animals consume them, does this provide a significant source of sustenance for them?


Oh, and here is another interesting wild habitat observation that has an aquarium correlate:

When leaves fall into streams, field studies have shown that their nitrogen content typically will increase. Why is this important? Scientists see this as evidence of microbial colonization, which is correlated by a measured increase in oxygen consumption. This is interesting to me, because the rare "disasters" that we see in our tanks (when we do see them, of course, which fortunately isn't very often at all)- are usually caused by the hobbyist adding a really large quantity of leaves at once, resulting in the fishes gasping at the surface- a sign of...oxygen depletion?

Makes sense, right? 

As I've said repeatedly, if we don't make the effort to try to understand the "how's and why's" of Nature, and attempt to skirt Her processes- she can and will kick our asses! The aforementioned is a classic example of how something which occurs in Nature also occurs in our aquariums- with profoundly negative results if we don't understand the implications.

These are interesting clues about the process of decomposition of leaves when they enter into our aquatic ecosystems. They have huge implications for our use of botanicals and the way we manage our aquariums. I think that the simple fact that pH and oxygen tend to go down quickly when leaves are initially submerged in pure water during lab tests gives us an idea as to what to expect. This is why we are so adamant about going slowly when adding botanicals and leaves to an established, stable aquarium.

And a sort of "set of expectations" is always nice to have when you're pursuing unusual approaches in aquarium keeping, right? It is- and that's why we've devoted so much time over the years towards educating our community about the potential issues which can arise if you flaunt Nature's "rules" concerning environmental changes in our tanks. 

A lot of the initial environmental changes in our aquariums will happen rather rapidly, and then stabilize over time. Which of course, leads me to conclude that the development of sufficient populations of organisms to process the incoming botanical load is a critical part of the establishment of our botanical-style aquariums.

We're at a point now- some five plus years into our journey at Tannin Aquatics, with hundreds of articles, social media posts, videos, and podcasts- that I feel it's time for each and every hobbyists to make use of this information and to accept responsibility for his or her decisions in utilizing botanicals in their aquariums. With the volume of information about once arcane topics now so readily available, there is simply no excuse for not taking the time to understand some of this stuff before jumping into this endeavor.

A bit of "tough love", but if you want to play- you need to know the rules, right?

Here's another thing to consider: Inputs of terrestrial materials like leaf litter and seed pods can leach dissolved organic carbon, rich in lignin and cellulose.  Factors like light, mineral hardness, and the bacterial community affect the degree to which this material is broken down into its constituent parts in this environment.

Or, if the resulting breakdown creates some "algae fuel"- right?

Hmm...something we've kind of known for a while, right?

Light+nutrient= algae growth.

Our botanical-style aquariums might look a bit different, and embrace a slightly different approach, but the same "constants" which apply to almost any other type of closed system aquarium apply to ours as well.

However, some things that we play with do seem to give very unique results. In botanical-stye, blackwater aquariums we're seeing more and more reports of "spontaneous" spawnings of all sorts of different fishes associated with these types of conditions.

Often, it's a group of fishes that the aquarist had for a while, perhaps with little effort put into spawning them, and then it just sort of "happened." For others, it is perhaps expected- maybe the ultimate goal as it relates to a specific species...but was just taking a long time!

The "common denominator" in all of the reports we receive are that the fishes are displaying better overall color, vigor, and overall health after being recently exposed to the more "physiologically appropriate" conditions of a blackwater aquarium. Now, this is by no means us stating that blackwater/botanical-style tanks are somehow magical, and possess the ability to make every fish magically thrive and spawn- or that this is some amazing "secret" that we've stumbled upon.

Nope. It's as old as the hobby itself. Provide fishes the right conditions, and they will thrive and spawn. It's hardly magic.

Rather, it's part of of an affirmation of a theory which I've developed over the decades that fishes from specialized environments- even those which might be several generations captive-bred, can always benefit from being "re-patriated" to the conditions under which they have evolved for eons.

Of course, with botanical-style aquariums, we know that we have a few things going for us already.

I think there is a lot to be said for the potential benefits of humic substances for fishes- substances which are found in abundance in the natural botanical materials we play with-and indeed, much research has been done in this area already by science.

Still, much is yet to be fully understood, but suffice it to say, there are a variety of health benefits ascribed to humic substances found in blackwater and other  habitats, and the "superficial", yet numerous observations we've made thus far seem to confirm this!

What advantages do they give us when we're trying to breed fishes from these habitats?

One could generally state that they reduce stress, if nothing else, right? That's at least a start. It's long been known that fishes kept under conditions which minimize stress are healthier overall, and part of the overall health is that they will engage more readily in natural behaviors such as spawning.

DO botanical-style aquariums accomplish this?

I think so. However, I'll be the first to admit that we're still learning about this stuff, aren't we? So to draw anything more than the most superficial conclusion is just speculative.

And some of that "research and development" comes from looking at the wild ecosystems of the world, and figuring our how to replicate them on a deeper level. It's all very exciting. Very interesting...And very much in the tradition of the aquarium hobby.

Keep after it. 

Stay enthusiastic. Stay diligent. Stay resourceful. Stay persistent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


Leave a comment