Don't keep up the fight...

Gear, specifically filters, keeps a lot of hobbyists- and manufacturers-quite busy as they wrap their heads around which ones are the best to use in botanical-method aquariums. I get this question constantly. The reality is that you can use pretty much any type of filter available for aquariums...or none at all.

Well- more specifically-you could actually use the tank itself; essentially, the botanical environment as the "biological filter", and simply use aeration/surface skimming and/or circulation pumps to facilitate the gas exchange. This is not revolutionary, of course- but an idea that's often overlooked today. We're obsessed with having big, bad-ass filters, loaded with media, to "polish" the water, exactly?

To fight Nature? Because that's what a lot of this stuff actually does, when you really think about it. It's to "correct" stuff that is "out of balance" or whatever...right?

I mean, we've been told for generations that filters remove solid, chemical, and biological waste from our aquarium water..I mean, they do...but they don't do it without attention and regular maintenance. Filter media get clogged, chemical media become exhausted, and impellers and intakes need cleaning.  And they don't just take out "bad" stuff- they remove..."stuff"- indiscriminately- and some of which is required to be present in the aquarium in order  to have an ecologically functional aquarium.

I can't help but wonder if we've come so under the spell of technology that a good percentage of hobbyists are 100% convinced that you can't run a successful aquarium without a fairly sophisticated filter-or some kind of filter, at least.


I beg to differ, of course.


And the sad reality is, I think that a lot of aquarists simply cannot run their tanks without very capable filtration. It sounds harsh, but based upon the number of tanks I see on Facebook groups and forums, where hobbyists are posting that they are struggling to keep their tanks "clean", I'd say that we have created a sort of strange "dependency" on the technology of filters.

It goes hand-in-hand with a disdain for- and dependency on water exchanges, and heavy siphoning of "detritus" and such from our tanks, as we're apparently convinced  that any amount of this stuff accumulating in our tanks is a recipe for certain disaster. We've  made it a real "chore", and have turned water exchanges into an urgent, yet loathsome process that literally keeps our tanks from teetering over the edge towards disaster!

As a hobby, I think that we've been so aggressive at keeping our tanks "near sterile" that the importance of water exchanges has shifted from a means to re-introduce a fresh "suite" of trace elements and remove a few residual organics into an essential way to remove liquid and solid wastes from our tanks.

We're obsessed with sterility and in doing so, we regularly wipe out the population of beneficial organisms which keep our tanks functioning biologically.

Aesthetics first has created this weird dichotomy.

Like, people on social media will ooh and awe when pics of beautiful wild aquatic habitats- many of which absolutely nothing like what we do in aquariums- are shared. They'll comment on how amazing Nature is, and admire the leaf litter and tinted water and stuff.

Yet, when it comes time to create an aquarium, they'll almost always "opt out" of attempting to create such a tank in their own home, and instead create a surgically-sterile aquatic art piece instead.

I think it's because we've been convinced by...well, almost everybody in the hobby- that it's not advisable or practical- or even possible- to create a truly functional natural aquarium system. It's easier to look for the sexiest named rock and designer wood and mimic some "award winning" 'scape instead.


I think that many hobbyists have lost sight of the fact that there are enormous populations of organisms which reside in their aquariums which process, utilize, and assimilate the waste materials that everyone is so concerned about. We've become convinced that technology is our salvation.

The reality is that a convergence of simple technology and embracing of fundamental ecology is what make successful aquariums- well-successful. In many cases (notice the caveat "many"...) you don't need a huge-capacity, ultra-powerful filter to keep your tank healthy. You don't need massive water exchanges and ultra meticulous water exchange/siphoning sessions to sustain your aquarium for indefinite periods of time.

What you need is a combination of a decent filter system, a regular schedule of small simple water exchanges, and a healthy and unmolested microbiome of beneficial organisms within your aquarium. 

I've touched on this hundreds of times in "The Tint: and elsewhere, but I think that we as a hobby have sort of forgotten some of the fundamentals of aquarium management, function, and process, and somehow glorified acquiring pricy gear and implementing draconian procedures as the "standard operating procedure" for running successful aquariums. We've left the idea of the aquarium-or more specifically, the microbiome of organisms within the aquarium-helping to create optimized conditions for our fishes- somewhere in the misty past of the hobby.

In the botanical-method aquarium, ecology is 9/10's of the game. Think about this simple fact:

The botanical materials present in our systems provide enormous surface area upon which beneficial bacterial biofilms and fungal growths can colonize. These life forms utilize the organic compounds present in the water as a nutritional source.

Oh, the part about the biofilms and fungal growths sounds familiar, doesn't it?

Let's talk about our buddies, the biofilms, just a bit more. One more time. Because nothing seems as contrary to many hobbyists than to sing the praises of these gooey-looking strands of bacterial goodness!

Structurally, biofilms are surprisingly strong structures, which offer their colonial members "on-board" nutritional sources, exchange of metabolites, protection, and cellular communication. They form extremely rapidly on just about any hard surface that is submerged in water.

When I see aquarium writings in which biofilms are considered a "nuisance", and suggestions that it can be eliminated by "reducing nutrients" in the aquarium, I usually cringe. Mainly, because no matter what you do, biofilms are ubiquitous, and always present in our aquariums. We may not see the famous long, stringy "snot" of our nightmares, but the reality is that they're present in our tanks regardless.

And it's perfectly fine.

The other reality is that biofilms are something that we as aquarists typically fear because of the way they look. In and of themselves, biofilms are not harmful to our fishes. They function not only as a means to sequester and process nutrients ( a natural "filter" of sorts?), they also represent a beneficial food source for fishes.

Now, look, I can see rare scenarios where massive amounts of biofilms (relative to the water volume of the aquarium) can consume significant quantities of oxygen and be problematic for the fishes which reside in your tank. These explosions in biofilm growth are usually the result of adding too much botanical material too quickly to the aquarium. They're excaserbated by insufficient oxygenation/circulation within the aquarium.

These are very unusual circumstances, resulting from a combination of missteps by the aquarist.

Typically, however, biofilms are far more beneficial that they are even remotely detrimental to our aquariums.

Yeah, they're really quite useful as a form of biological filtration.

Nutrients in the water column, even when in low concentrations, are delivered to the biofilm through the complex system of water channels, where they are adsorbed into the biofilm matrix, where they become available to the individual cells.  Some biologists feel that this efficient method of gathering energy might be a major evolutionary advantage for biofilms which live in particularly in turbulent ecosystems, like streams, (or aquariums, right?) with significant flow, where nutrient concentrations are typically lower and quite widely dispersed.

Biofilms have been used successfully in water/wastewater treatment for well over 100 years! In such filtration systems the filter medium (typically, sand) offers a tremendous amount of surface area for the microbes to attach to, and to feed upon the organic material in the water being treated. The formation of biofilms upon the "media" consume the undesirable organics in the water, effectively "filtering" it!

Biofilm acts as an adsorbent layer, in which organic materials and other nutrients are concentrated from the water column. As you might suspect, higher nutrient concentrations tend to produce biofilms that are thicker and denser than those grown in low nutrient concentrations.

Those biofilms which grow in higher flow environments, like streams, rivers, or areas exposed to wave action, tend to be denser in their morphology. These biofilms tend to form long, stringy filaments or "streamers",which point in the direction of the flow. These biofilms are characterized by characteristic known as  "viscoelasticity."This means that they are flexible, and stretch out significantly in higher flow rate environments, and contract once again when the velocity of the flow is reduced.

Okay, that's probably way more than you want to know about the physiology of biofilms! Regardless, it's important for us as botanical-method aquarists to have at least a rudimentary understanding of these often misunderstood, incredibly useful, and entirely under-appreciated life forms.

And, as we already mentioned, the whole idea of facilitating a microbiome in our aquariums is predicated upon supplying a quantity of botanical materials- specifically, leaf litter, for the beneficial organisms to colonize and begin the decomposition process. An interesting study I found by Mehering, et. al (2014) on the nutrient sequestration caused by leaf litter yielded this interesting little passage:

"During leaf litter decomposition, microbial biomass and accumulated inorganic materials immobilize and retain nutrients, and therefore, both biotic and abiotic drivers may influence detrital nutrient content."

The study determined that leaves such as oak "immobilized" nitrogen. Generally thinking, it is thought that leaf litter acts as a "sink" for nutrients over time in aquatic ecosystems.

Oh, and one more thing about leaves and their resulting detritus in tropical streams: Ecologists strongly believe that microbial colonized detritus is a more palatable and nutritious food source for detritivores than uncolonized dead leaves. The microbial growth which occurs on the leaves and their resulting detritus increases the nutritional quality of leaf detritus, because the microbial biomass on the leaves is more digestible than the leaves themselves (because of lignin, etc.).

Oh, I'm going on and on about this stuff- but the idea of the aquarium, or more precisely, the microbiome of the aquarium- acting as a "filter"- is worth considering. You could successfully run a botanical-method aquarium without a "filter" of any kind, other than the materials contained within the tank itself. 

I mean, this isn't really an earth-shattering concept.

Every fucking tank in the 19th century, and many in the early 20th century, ran this way, right? Yeah. Now, I get it- these were tanks which were often dominated by aquatic plants, which processed the nutrients and realized oxygen via photosynthesis, but the idea here is essentially the same- creating a biological system which assimilates and processes nutrients. Our "Urban Igapo" tanks use terrestrial or riparian plants...they uptake nutrients from the soils...

Yet, there are other organisms besides plants to accomplish nutrient export, right? Now, what about our old nemesis, cyanobacteria- that stringy stuff we've been taught to loathe over the years? Well, they're photosynthetic. They convert sunlight into energy and produce oxygen as a waste product. Maybe cultivating them in our "filterless" tanks could be a cool idea, huh?


Look, the reality is this: By making the effort to understand and cultivate the life forms that live in the aquatic environment, and embracing the work they do, we can have remarkably successful aquariums. When we utilize filters as a means to supplement what Nature does, it gets really interesting.

It doesn't make you some kind of renegade to take this position.

And the reality is that I think the most valuable function of most filters is to create water movement, or to facilitate surface agitation. Oh sure, they can pull out some suspended debris, too...if that's a real problem.

Now, don't get me wrong- I love activated carbon, PolyFilter, etc. and chemical media. I love efficient filter systems. But the reality is that 90% of my freshwater aquariums rely primarily on the ecology within the tank to help keep things going healthily. That's the "filter system." My sumps and all-in-one tanks usually have no filter media at all in them. And I don't embrace this whole "botanical method" of aquarium keeping as a means to preach to avoidance of keeping our tanks healthy and attractive. Rather, my obsession is with getting us all to think about Nature as a "partner" to work with, as opposed to an adversary to try to keep at bay. 

Just because some of Nature's most important ecological functions may look a bit "different" than we'd want them to doesn't mean that they are somehow "bad." That's the one thing I hope that many hobbyists can eventually absorb. It's so vital, and I think will create more of a sense of working with our tanks- and with natural processes, instead of creating a zombie-like adherence to executing infrequent massive water exchanges/siphoning sessions and a reliance on expensive equipment to convince ourselves that we're doing the ultimate to manage our tanks efficiently.

Learning about achieving a balance through process, practice, and equipment is a simple way to dramatically improve your aquarium hobby experience. If we spend less time shopping for that "perfect" filter sand more time reading about say, food webs or the dynamics of nutrient processing in aquatic ecosystems, I think that the net result would be more happy hobbyists doing cooler and more progressive stuff!

Siphoning out, scrubbing, and polishing away these misunderstood natural byproducts is often so counterproductive. We have spent decades fighting Nature and probably not even realizing it. Time to really understand Her and "make nice!"

Hug it out with Mother Nature. Stop the fight!

Stay thoughtful. Stay curious. Stay bold. Stay efficient. Stay creative. Stay observant...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


1 Response


December 21, 2021

Hello Scott

I’m new into this hobby (my aquarium has less than a year). I want to congradulate you for this article. Before buying the aquarium and the fishes i did some research. (related to fish and snails, heater, filter and so on). As you mentioned 99% of the information available say we need filter. In the last few days i saw a video where they also said a filter is not needed (they were using a deep substrate).

Thank you once again

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