The musings of a leaf litter nerd...

There is always something exciting about going on an adventure in the hobby. Taking an idea and running with it...Researching a concept. Playing a hunch...

If you've been reading my blogs here over the past couple of years, you know that I've been throwing out a lot of crazy ideas. Some seem to come up more often than others. Case in point:

I periodically discuss the idea of creating a really deep litter bed in an aquarium, to more accurately replicate some of the litter beds found in South America and elsewhere. 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?

Now, there is certainly a difference between the "theoretical" and the "practical", but I can't help but think that there is something beneficial about such a deep leaf litter bed...perhaps stuff we haven't imagined, because we're too busy talking about tall of the possible "downsides" of the idea. And it's intriguing for me to contemplate how to make such an idea work. I mean, it isn't really all that much different than what many of us do now...the main difference being that we'd use MORE of the same materials.

In researching the idea of executing such a deep litter bed, I thought about what would be the main considerations when attempting to create one in an aquarium. In no particular order, here are just a few of the main concerns I have:

-The ratio of "leaves to water" in a given aquarium could be quite significant. I mean, what size aquarium do I go with? I'm also curious about the impact on the water quality and oxygen levels with that much decomposing materials "in play." On the other hand, starting from scratch with a system and cycling it with "bacteria in a bottle" products and/or "seeded" substrate materials would no doubt at least "kick start" the biological filtration before fishes ever enter the equation.

And, although the mass of leaves would be considered "bioload", I can't help but wonder if it would also 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? Like, denitrification by "deep leaf litter bed!"

And what about the impact on pH?

There have been researchers of natural leaf-litter banks who contemplate that processes which produce the low pH levels associated with these beds (sometimes down to 2.8-3.5pH!) are not caused entirely by humic acids which are frequently assumed to be the major contributor -and are not strong enough acids to produce such a low pH. A possibility suggested by researchers is that fermentation within the litter banks is releasing strong organic acids such as acetic acid...Could this happen in the confines of a closed aquarium?

-Would you use a traditional substrate material in addition to the leaves? I'm thinking that it makes sense to use a typical sand material with a minor amount of buffering capability. Using straight-up RO/DI water and having a huge component of tannin-and-humic-substance-producing leaf materials would certainly have an influence on the pH, and some buffering would perhaps be wise to keep the pH in a manageable range, I'd think. So, perhaps a thin layer of sand at the bottom of it all makes some sense...

-Water movement is something I don't take for granted. As a reef aquarist, I came to understand that water movement is as important as components such as light and feeding, and I feel it's vital to freshwater fishes as well. In this case, the movement of water 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). This is, of course, a hypothesis, and only testing will determine if this is ultimately an issue. The oxygenation issues occurring deep down in the litter bed is something I haven't thought too much about, but probably should. Oh, and it keeps those annoying bits of decomposing leaves in the water column to facilitate easy removal!

"Oxygenation issues?" Like, "Low oxygen levels in the litter bed?" I would imagine that fishes not accustomed to such an environment should instinctively avoid it, and others might be simply 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." (These species are in the families of Auchenipteridae, Doradidae, Cetopsidae, Heptapteridae, Trichomycteridae, and Pseudopimelodidae)

-And of course, there is the practicality component for us: Maintenance.  Okay, we all understand the value of water changes, and I am a huge proponent of them. No issues here. On the other hand, 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?

And, in such a deep layer of leaves, is it advisable to replace them on a more frequent basis to prevent maintenance liabilities? For that matter, are decomposing leaves on this scale a "maintenance liability?" Something tells me that, much like we've vilified "detritus" over the years, decomposing botanical materials may not be the "bogeyman" that we think they are. Could they be considered a "carbon source"- the freshwater equivalent of "biopellets"- to fuel beneficial bacterial growth within the system, creating excellent nutrient processing capacity... as opposed to being some sort of "destroyer" of water quality?

Could we be missing something? Could it actually be that a deep layer of botanicals/leaves is actually a key to creating a biologically stable aquarium, once you reach a certain depth, if the overall husbandry of the tank is good? Maybe? Now, I've never had any issues with a relatively small, open layer of leaves in any of my tanks (we're talking 1"-3" /2.54-7.62cm) or so. I just wonder if the dynamic changes significantly- for the better- or worse- when you approach a foot of depth in an aquarium?

Something we'll just have to see, I suppose!

-Would it make sense to include bottom-dwelling fishes (like Crenuchus, Elachocharax, and various catfishes), or is it best to keep any fishes that could disturb the litter bed out? Nah..My immediate thinking is that I should ABSOLUTELY include fishes that live within the void spaces in the leaf litter matrix...What would be the point of excluding them and only having a bunch of schooling tetras and such above this unique feature,, right?

Yeah! No issue here, IMHO.

Obviously, these are just a few of the questions I have regarding this type of setup. There are numerous others, ranging from what type of filtration I'd use to how much light intensity you'd want to apply. All are important and fun to ponder. As with many things in the aquarium world, I can't help but wonder if so much of what's been drilled into our heads over the generations about what is and is not "acceptable" is still open to debate? I mean, in our little blackwater niche alone, I think we've killed off some "rules"-seen a lot of experimentation with, and successful implementation of- practices that would have simply made earlier hobbyists freak the #&%$ out!

Because we did something instead of simply dismissing it outright as "dangerous" or "reckless."

However, in the end, taking on something like this requires us as hobbyists to get out of the theoretical and into the practical at some point, right? There is always room (and need) in this hobby for responsible experimentation on new ideas.

I know I'm certainly not the first to think about the implications of a seriously deep leaf litter bed in an aquarium, but you'd be surprised (or maybe not, actually) at the lack of useful hobbyist-level information out there on the subject! This is a classic example of why I feel it's so important to discuss these types of adventures with fellow hobbyists, even when they're in the hypothetical or planning phases. Your ideas- your experiences- just might move someone else to take the next step.

The step that could yield the "big breakthrough.."

...Or the next total disaster. Yeah. That's always a possibility. Always part of the game.

Moving from the theoretical to the functional takes some courage, imagination, and most of all..impulse. When it comes to trying out exotic new concept aquariums, guys like me (as you all know by now) just need to get the damn thing started and stop musing on about it. Others go full speed ahead...damn the torpedo! Regardless, self-awareness is important! I think it's in my nature to get a bit too deep into the planning. The challenge for me is not to get so bogged down in an endless cycle of "analysis paralysis" that I never get projects off of the drawing board! 

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. Stay undeterred.Stay active...

And Stay Wet!


Scott Fellman

Tannin Aquatics

Scott Fellman
Scott Fellman


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