Musings on the "botanical influence" in our tanks...

If you've been reading my blogs here, you know that I've discussed the idea of creating a really deep litter/botanical bed in an aquarium for the last few months, to more accurately replicate some of the litter beds found in South America and elsewhere. And a number of you have really jumped on the idea, too. Oh, by "deep", I'm talking 6"- 12" (15.24cm-30.48cm). Yes, there are deeper litter beds in these areas (several feet in depth); however, for practical aquarium display purposes, I think the rational "upper limit" is more like the 12" (30.48cm) range. Or is it?

There seems little doubt that the abundance of leaf litter in the tropical environments that we're obsessed with replicating in our aquariums have profound impact on the variety and life cycle of tropical fishes, so it's been an irresistible subject for us to play with.


And, although the mass of leaves would be considered "bioload", I can't help but wonder if it we're seeing these deep botanical beds and dense botanical/hardscape "matrixes" function as a nutrient processing facility, much in the same way a deep sand bed does in a reef aquarium? I mean, with that much "media" surface area, could this be the case?

We've seen bold adventurers, like JT Martin, create beautiful and functional aquariums by "going deep"- and there certainly have been some discoveries- and challenges- along the way! We definitely are getting a larger body of work from which to create a  hypothesis as more and more of you play with "botanical bottoms!"

We've learned to add materials gradually- or, at the very least, to allow the system time to adjust to our "introductions" of new leaves and other botanical materials, as a rapid, large influx of botanicals can affect things like dissolved oxygen levels and such, which certainly affect our fishes!

I've thought a lot about TDS lately. Using RO/DI water and having a huge component of tannin-and-humic-substance-producing leaf materials would certainly have an influence on the TDS. I know personally that you will see interesting TDS readings after adding botanicals. My water starts at 0 TDS (pure RO/DI) right out of the unit. I haven't been "remineralizing" it. In my the aquarium, the TDS level rose initially when I set up the tank  to about 24, until ultimately "stabilizing" itself at about 20. It's been "pinned" there ever since. I have always been a "gradual adder" of botanicals, so I don't see much deviation from these values...but the trend is interesting. Curious about your experiences with TDS.

Water movement is something I don't think we, as botanical/blackwater enthusiasts, can take for granted. As a reef aquarist, I came to understand that water movement is as important a part of the equation as components such as light and feeding, and I feel it's vital to freshwater fishes as well, particularly in heavily-botanical-laden systems. Large quantities of decomposing botanical materials have some oxygen demand on the system, and when you add a large influx of materials in a relatively short span of time, there's bound to be some significant affect on the environment.

To help positively impact the environment in botanical tanks, water movement is really important, as it will prevent areas of stagnation, low oxygen, and perhaps pH "striation", with areas of less movement having extreme pH levels (on the low side). Surface disruption is important, IMHO.  Your fishes will let you know if you've pushed it to far, as those of us who have can attest!

On the other hand, fishes might be able to adapt to it. Indeed, a study I read (Walker, et al) on deep leaf litter beds in the Amazon region found that "Several...species show adaptations for living under low oxygen conditions, which possibly allow them to occupy confined spaces inside the banks."  I'd like to see more bottom-dwelling fishes (like Crenuchus, Elachocharax, and various catfishes) that are known to inhabit the litter beds. In fact, I'd like to see a dedicated leaf-litter-bed fish aquarium!  

And of course, there is the "practicality" component:  Maintenance.  Now, we all understand the value of water changes, and I am a huge proponent of them. Just how much to change, and where to siphon is of interest to me. I can't help but play "devil's advocate" at times, and consider this:  With a lot of leaf material breaking down, and possibly trapping detritus and other organic materials (gross particulate matter, mainly), will siphoning out the decomposing leaf material be the best approach, or are the deeper layers best left undisturbed? I've always sort of done a light siphoning of the surface laters of my "botanical bed", removing any visible offensive detritus or debris that I don't want in the tank, and this practice has served me well.

You had us all the time tell you to consider leaves as "consumables", much like carbon or filter media- requiring regular replacement. I personally think that it's advisable to keep replacing leaves on a more frequent basis to keep things sort of stable. In a really deep botanical bed, I wonder if there is any stability difference when you approach a foot of depth in an aquarium? Something we'll just have to see, I suppose, as more of you play with the concept of deeper beds. It will also be useful to note if different materials are more functional than others for such applications.

We definitely need to track environmental parameters and note the overall function and dynamic of our deep botanical-bed systems over the long haul, as this can yield valuable information and inspire others to try new experiments themselves!



As we play with more and more new ideas, and gain greater confidence and understanding, it's fun to see the cool things everyone is playing with. What exotic, unusual, or otherwise seldom-attempted aquariums are you contemplating? And what challenges or questions do you ponder?

Whatever your course is...stay on it. Stay bold. Stay creative. Stay curious.

And stay wet!

Scott Fellman

Tannin Aquatics

Scott Fellman
Scott Fellman


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