The stability factor.

When it comes to keeping and maintaining our botanical-style aquariums over the long term, there are a fair number of questions we receive regularly, so it kind of makes sense for us to tackle this topic once again.

Now, one thing to just contemplate before we delve too deep is just this whole concept of the botanical-style aquarium...I mean, like, we keep an aquarium stocked with leaves, seed pods, and other stuff in order to...what?

Well, for most of us, it's stocked with this stuff in order to replicate, on some level, the environmental, chemical, and physical environments from which our fishes come from in the wild. And since the wild is not the sterilized, crystal-clear, sparkling clean place of "Nature Aquarium" fantasy, we have to think about things a bit differently.

The whole idea of this kind of system operates on a sort of "contrarian" mindset, which is very different than what we have been "conditioned" to accept in the aquarium hobby. Again, just sort of wrap your head around this for a minute: You're not talking about siphoning out every speck of detritus, or worrying about every strand of algae, biofilm, or decomposing leaf. Crazy, right?

So, with an aquarium filled with this stuff, your first thought (and rightly so, I suppose) is, "Shit, this could go south really fast if I let it.."

Yet, I have a differing theory.

I think that the presence of these materials-particularly, leaf litter- serves as a "catalyst" or "fuel" for biological processes, such as denitrification. At least one field study of natural systems and the impact of leaf litter to facilitate aquatic habitat restoration concluded the same:

"...The benefits of leaf litter addition shown in our study, including enhanced microbial activity and denitrification processes..." (from O'Brian, et al. 2017)

It makes a certain degree of sense, really.

I can't help but think of the "biological processing capability" of leaf litter/botanical beds as a sort of freshwater analog to the "deep sand bed" or "refugium" concepts of the reef aquarium world. And sure, although we are talking about closed aquatic systems, Nature still controls things.

And everything we do- fish/ food inputs, maintenance, and nutrient export functions to create some sort of a "balance", right? You know- not bringing in too much nutrient without a correspondingly sufficient export process?

So, yeah- creating an aquarium using botanicals is about creating a balance.

And the maintenance practices we incorporate into our aquarium practices are all about maintaining that balance. And that starts with the most time-honored, basic, and easy-to-execute (yet oddly loathed by many...) maintenance practice:

Water exchanges.


First off, a lot of people ask me about doing water exchanges; specifically, how much, how often, and...HOW!

Okay, first off-let's be clear about one thing: There really is no "magic technique" to maintaining a (blackwater) botanical-influenced aquarium, other than the usual "stuff"- with a few variations.

So, if I had one key concept that is most important to get across, other than understanding that our aquariums require balance- it's about promoting stability.


Not really novel, I know...but think in terms of stability and everything else is pretty easy, right?

I personally think that environmental stability is one of the most important- if not THE most important- things we can provide for our fishes. To me, it's more about doing something consistently than it is about some specific practice.

I favor a 20% weekly water exchange in my aquariums. That may seem like a lot to some, but it's the regimen I've stuck with for decades, and it's never done me wrong. In a botanical influenced aquarium, as we all know, you've got a lot of biological material in there in addition to the fishes (you know, like decomposing leaves and softening seed puds- stuff like that), and even in well-managed, biologically-balanced aquarium, you still want to minimize the effects of any excess  organics accumulating in a detrimental manner. 

So, without going on and on and on, I simply will encourage you to embrace a weekly water exchange.

And of course, in the context of water exchanges, I'm always asked if we should remove broken-down bits of botanicals, leaves, and detritus during this process. I think that we certainly can remove this stuff if we want.  Shit, Scott- that's super helpful...

Yet I personally don't go crazy and try to remove every single milligram of the stuff from my tanks. We've talked repeatedly about my views on detritus, so I won't rehash it too much here, except to state that if you find this stuff offensive or aesthetically revolting in some way, take it out. However, if you fully embrace the view that Nature utilizes this material to serve as a means of processing nutrients and fostering denitrification, you might just want to leave some- or all of it- in.

Now, the caveat here is that I didn't just "give myself permission" to neglect tanks or avoid basic, that wasn't the point. The point is to accept that materials breaking down in our aquariums can provide "fuel" for the biological processes which create long-term stability in a closed system.

Nature knows how to work with this stuff. yet, make no mistake here:

She'll absolutely kick your ass if you don't pay attention to husbandry. I 100% guarantee it. Full stop.

Allowing plants, fishes, shrimp, and bacteria the chance to utilize the decomposing botanicals in their life cycle is an important part of the game, IMHO. Being overly fastidious about siphoning out every speck of dirt or botanical material as it breaks down is "overkill", in my opinion, and can be just as detrimental as over-doing things. 

Nature strikes a balance. Nature thrives on efficiency. When you're adding botanicals to a tank, you're not just doing "aquascaping"- you're laying down the groundwork for the "biological operating system" of your aquarium. As such, you need to think "big picture" here. (That "functional aesthetics" thing again!)

And there's the role of this stuff in regards to food.

Part of the "big picture" in our tanks is the idea that we can create  a "food web" of sorts- or at least, foster supplemental food sources by utilizing botanicals-allowing them to remain in the system.

Now, ruminate on this for just a second...

Ever think about what your fishes eat in the wild? But beyond that, what implications do their dietary preferences have for those who want to mimic them as closely as possible?

Yeah, it's easy to say "insects and stuff" and just move on, but the reality is that, even for some of the most unlikely fishes, the variety of items they consume is astonishingly diverse, and perhaps a bit unexpected!

Of course, I had to get down and dirty and do some online research...And I found some interesting stuff. For example, one study of the gut contents of that rather well-liked characin, the Cardinal Tetra (Paracheirodon axelrodi) in it's natural habitat yielded some familiar food items, and perhaps, a few surprises:

Harpactoid copepods (you know, like the kind we use as food for marine fishes), Daphnia, Moina (another small, Daphnia-like microcrustracean), nymph larvae,  small flies of various species, partially digested ants (!). In addition to being a surprising find, the presence of ants and flies in the fishes' digestive systems confirms that they may feed from the surface in the wild, too! Clumsy ants don't last too long in those flooded forests...

Remember, allochthonous input?

Those flakes and pellets we toss in are recognizable to these guys, perhaps not because they physically resemble natural foods or smell good, but because they facilitate natural feeding behaviors ingrained in the fishes for eons: Yeah, these fishes will dart to the surface and feed in the wild, so...

What else did the study find?

Rotifers, crustacean larvae, and crustacean and fish eggs, some filamentous algae and diatoms were also found, further bolstering the idea that although we tend to classify fishes like characins as "micro predators." They are also opportunistic ominivores to some extent, foraging for what they can in the environments in which they reside. And, then, there is also random "detritus", including things like fish scales, decomposed leaf material and such. And the presence of fish scales- which you could hypothesize might mean that they either pick at other fishes, or forage on dead ones...yuck- confirms the "opportunistic" part. This stuff comprises a fair amount of their gut contents.

What does all of this stuff mean for us as hobbyists?

Well, I'm not saying to feed dead fishes to your tank, or to drop ants into your tank (although it is tempting, if not a bit vengeful, when your home is under siege from the little bastards...) as a huge part of your feeding regimen.

What I am saying is that a diverse menu of plant an animal material is always a good idea, and the bulk should be things like crustaceans, insect larvae (hey- bloodworms!), and even some of the live or frozen copepods, and stuff like Daphnia would make a diet that is a pretty good mimic of what they consume in the wild, right?

And maybe that old, yet annoyingly-messy-to-culture standby, the Wingless Fruit Fly, might not be a bad food source? And, I suppose ants, too!

Yeah, you bet! 

And those litter beds are perhaps one of the ultimate "culture media" for all of this stuff! And they are very much a "feeding ground" for fishes.

Another interesting thing I learned in my research was that when scientists studied some Amazonian leaf litter beds, it was found that, in one study, there were like 20-plus species found in one bed of like 200 square meters- a remarkable diversity considering the rather specialized environment. And perhaps even more interesting was that the bulk of the species found were feeding almost exclusively on the invertebrate life present in these liter beds, seldom straying more than one meter (!) from where they were initially captured.

Talk about going where the food is!

As there are finite resources of food, even in an area as productive as a submerged leaf litter bed, and because there is such a diversity of species in such a small area, it was theorized by researchers (Henderson and Walker) that fishes have developed what they termed "refined habitat subdivision." In simple terms, this means that each species has evolved to feed on a separate resource supply to avoid "competitive deprivation" of the food sources.

The prey doesn't move, either- like chironomids (an insect-like creature) that comprise a lot of the fishes' diets, remain attached to the same leaf for their entire life cycle! So you see where this is going? Each fish inhabits a spatial niche within the litter, feeding on it's own "localized" food supply.

Well, at least I found this interesting!

Again, what are the aquarium-level takeaways here? Well, since we can get food to our fishes regardless of what level they inhabit within our aquariums, it is entirely logical to create fish communities where the species selected inhabit different areas of the tank (okay, leaf litter bed, in my obsessive fish-geek case). So for example, a good combination of fishes in a leaf-litter-themed tank would include Apistogramma, which in nature seem to hang out at the edges of the leaf litter beds, various characins in the "middle" of it all, and fishes like Pencilfishes and Pyrulina holding station above the litter bed (I see this in my own tanks).

If one could ever secure my obsession fish, the cryptic, darter-like characin, Elachocharax pulcher, they'd reside right smack in the middle of the leaf litter! Ahh..

Okay, so anyways, to wrap up this meander- you can see that feeding is just one consideration you can think about when creating, stocking, and maintaining a botanical-style aquarium. Not only what to feed, but where...

Think about preferred feeding niches for various species in the wild when selecting fishes for your tanks! Now, granted, in an aquarium, fishes will adapt and typically  feed wherever the food is- but wouldn't it be an interesting experiment to set up a population of fishes that you know feed in different locales, and actually creating those locales for the fishes? Maybe? No? Possibly?

Okay, whatever. I'm obviously geeking out here about this stuff...

Yeah, so wrap all of these concepts and ideas together in the context of creating long-term stable botanical-style aquariums, and it comes back to the overriding concept of creating and maintaining stability.

Detritus. Decomposing leaves. "In situ" food sources. Regular water exchanges.

Incorporating and embracing all of these elements into our botanical-style aquarium "practice" is foundational, IMHO.

Yeah, it's indicative of another "mental shift" we have to make, I which many of you have already made, no doubt. I certainly look forward to seeing many examples of us utilizing "what we've got" to the advantage of our fishes! 

Stay consistent. Stay curious. Stay diligent. Stay creative. Stay persistent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 




Scott Fellman
Scott Fellman


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