February 14, 2020

Leaves, experiments, and subtle evolutions...

The concept of botanical-style aquariums is more than just some passing "fad", or today's "hot number." Well, to me it is, anyways. The idea behind this movement is that there is more to a unique aquarium than just tossing in some unusual leaves, wood, etc. and working on a "style."

It's as much about function as anything else. And, about pushing into some new directions. The unorthodox aesthetics of these unusual aquariums we play with just happen to be an interesting "by-product" of their function.

The desire to question "status quo" and try to do things differently than the way we've always done them in the hobby often leads us down some paths that, although seemingly not that complicated or exotic, shun convention enough to be considered "evolutionary" steps. Ones that, if built upon further, may definitely lead into some completely new directions.

I'm obsessed with the idea of leaves and leaf litter beds in aquariums.

That's no secret.

From day one here at Tannin, we've talked up the idea of creating leaf litter beds in our tanks. We've touted the process, the looks, the benefits. And it all makes a lot of sense, really. Leaf litter beds are perhaps some of the most natural, abundant, and (surprisingly) aquarium-replicable habitats we can work with.

Nature provides all of the inspiration that we need to work with this idea.

My obsession with leaf litter started when I took a much closer look at these habitats, and considering how fishes live within the leaf litter in Nature. Understanding the way these habitats support the abundance of fishes and other life forms led to a real epiphany of sorts for me.. I realized that this type of habitat is not only relatively simple to recreate in the aquarium- it also performs the dual role of creating "functional aesthetics!"

One of the more fascinating scientific observations I stumbled upon in recent years concerts the productivity (in terms of food inputs) of Amazonian streams. It's long been known by science that the primary production of food in these streams has been our friend, allochthonous inputs- you know, leaves, wood, fruits, blossoms, etc. from the surrounding forests.

Now, although there is a lot of the "stuff" in these streams, interestingly, biologists tended to classify these habitats as "low in biomass."

However, recent studies of the microfaunal diversity of these streams (Walker and Feriera), it was found that the stream fauna was aggregated in submerged litter and "may reach considerable densities..." This observation suggested that the animal community within the submerged leaf litter banks was of greater importance to the productivity of these waters than previously believed.

In other words, a lot of life-and food- happens in submerged leaf litter beds!

They provide both food and shelter- two primary factors affecting population density among fishes. And, if we carry this out to its logical "aquarium interpretation", it becomes more intriguing to contemplate an aquarium with the "hardscape" (for want of a better word) consisting essentially (or completely) of leaves!

One of the more fascinating scientific observations I stumbled upon in recent years concerts the productivity (in terms of food inputs) of Amazonian streams. It's long been known by science that the primary production of food in these streams has been our friend, allochthonous inputs- you know, leaves, wood, fruits, blossoms, etc. from the surrounding forests.

And, although there is a lot of the stuff in these streams, biologists tended to classify these habitats as "low in biomass." However, recent studies of the microfaunal diversity of these streams (Walker and Feriera), it was found that the stream fauna was aggregated in submerged litter and "may reach considerable densities..."

This observation suggested that the animal community within the submerged leaf litter banks was found in greater abundances- and was of greater importance- to the productivity of these waters than previously believed.

In other words, a lot of life and food happens in submerged leaf litter beds! They provide both food and shelter- two primary factors affecting population density among fishes. If we carry this out to its logical aquarium interpretation, it becomes more intriguing to contemplate an aquarium with the "hardscape" (for want of a better word) consisting essentially of leaves!

Now, this is an idea that we have played with before. If you recall, last year, we constructed an aquarium in which the entire "structure" consisted of about a 1.5" (3.81cm) bed of Texas Live Oak leaf litter, a few Oak twigs...and that was it. A fine sprinkling of sand (like .25"/0.635cm) covered the very bottom of the aquarium.

I selected the Texas Live Oak leaf litter because it is one of the more "diverse" leaf products we work with- it contains bits of other terrestrial soils, dried mosses, small twigs, and even other types of small leaves. This makes it a very fertile "media" upon which to build an active, dynamic aquatic ecosystem in the aquarium. You could just as easily use Red Mangrove, Jackfruit, etc.

And this aquarium ran incredibly successfully!

And it was interesting too, fro man aquarium function perspective. There was virtually no traditional "cycle time"-curiously. And even more interesting, the tank stayed super "clean" in appearance. It did recruit some visible biofilm on the leaf surfaces, although it never really "bloomed" significantly after the first few weeks, and waned on its own in less than a month.

The other interesting thing about this tank is that I ran it as a sort of "proof of concept" tank, by allowing the litter to sit for a number of weeks without fishes, seeding it with a cup of decomposed leaf litter/botanicals from a different tank, some pure Paramecium cultures, some Daphnia, and some black worms to sort of "kick start" the micro/macro fauna population. I let it "run in" for about 3 weeks before adding fishes.

My goal was quite bold: To run an aquarium without any supplemental feeding of the resident fishes.

I populated the tank carefully, with 18 "Green Neon Tetras" (Paracheirodon simulans) as the sole occupants. I selected these fish because: a) they are small fishes with little production of waste, and b) they are efficient "micro predators" of small life forms, including the aforementioned Paramecium, biofilms, fungal growths, etc.

So, from day one, I didn't feed anything to these fishes. Rather, I let them do what they've done for eons in Nature- forage among leaf litter for their sustenance.

And it worked fabulously. (if I say so, myself!)

I started with 18 young, healthy specimens , and when I ended the experiment some 6 months later, I still had 18 healthy specimens- just as fat (if not, MORE so) than when they were added. And, at around three months into the experiment, they spawned! I personally take that as a measure of success!

Of course, despite my successful experiments In this "no-supplemental-feeding" realm, I have no illusions that the idea of just tossing fishes into an aquarium and letting them fend for themselves is some panacea and "ultimate" way to keep fishes. Nope. And, I did perform routine weekly water exchanges and regular filter cleanings (I used an Ehiem 2211). Nothing crazy there. And certainly not anything that would even qualify as "benign neglect", either. There was definitely not anything close to that. Interestingly, there was no detectible nitrate and phosphate in this aquarium during the entire operational lifespan of the system.

Other than no supplemental feeding, there was little more to distinguish this approach from more traditionally-run systems. However, I think it helps prove, to some extent, that there is a "low-maintenance, low food-input" aquarium approach for keeping certain small fishes which is viable.

Of course, that means setting the system up correctly from day one to function in this fashion.

Much like in Nature, if properly conceived and populated with an initial population of live food sources, I believe that an aquarium can be configured to create a productive, biologically-sustainable system, requiring little to no supplemental food input on the part of the aquarist to function successfully for extended periods of time. Of course, it is significantly different than a natural, fully-open system in many ways. And this is not a "revolutionary" statement or pronunciation, or some "breakthrough" in the art of aquarium keeping.

No.

It is just an idea that- like so many we encourage here- replicates some aspects of natural aquatic systems. With responsible management and continued experimentation, I really see no reason why this concept couldn't be done on a larger scale with the same great success.

My next experiment will be to apply this idea to a tank with a significantly deeper leaf litter bed- something like 3"-4" (7.62cm-10.16cm), to see if there are different possible outcomes with a greater leaf biomass. I am very curious to see if a deeper leaf litter bed functions similarly to the shallow type if regular maintenance is employed.

I suspect there will be not much difference in "performance."

My hypothesis is that it will, although for some reason, I am expecting to see a greater appearance of biofilms/fungal growths on the litter mass (the "more fuel/more fire" theory!). It'll be interesting to see if nitrate and phosphate levels in a deep leaf litter system managed this way are any different.

I also have executed a few versions of this concept using a mix of leaves and twigs and small botanicals, with similar results.

These types of experiments represent a further exploration into a natural approach which embraces both the aesthetics and function of some of the compelling habitats that we love so much. My hope is that my simple efforts will inspire those far more learned/talented than I to look at Nature, and interpret many of its aspects with a bent towards pushing ourselves in terms of management, husbandry, and aquascaping.

A marriage of ideas, form, and function. In around, and above the leaf litter bed. One that leads to an eloquent, dynamic ecosystem which can provide beautifully for all of its inhabitants.

Just like what happens in Nature.