One of the things that we love the most about our botanical-style aquariums is that they evolve over time. We've discussed this idea many times, particularly the idea that botanical materials become a "working" part of your aquarium's ecosystem, as biofilms and fungal growths cover them and transform them.

Over time, in the botanical-style aquarium, wonderful  transformative things happen...Leaves begin to accumulate. Botanicals begin to break down. Detritus settles.

Aquatic soils and substrates dissolve their chemical constituents- tannins, and humic acids- into the water, enriching it. Fungi and micororganisms begin to feed on and break down the materials. Biofilms form, crustaceans multiply rapidly.  Fishes are able to find new food sources; new hiding places..If we're lucky, new areas to spawn.

Life flourishes in the botanical-style aquarium. 

The habitat has evolved- transformed by unstoppable, constant natural processes. They look-and function- just like they do in Nature. And I understand that not everyone can handle that.

I admit, I feel a bit sorry for these people who can't make the "mental shift" to accept the fact that Nature does her own thing, and will lay down a "patina" on our botanicals, gradually transforming them into something a bit different than when we started. When we don't accept this process, we sadly get to miss out on Nature guiding our tank towards its ultimate beauty- perhaps better than we even envisioned.

For some, it's really hard to accept this process. To let go of everything they've known before in the hobby. To wait while Nature goes through her growing pains, decomposing, transforming and yeah- evolving our aquascapes from carefully-planned art installations to living, breathing, functioning microcosms.

But, what about all of that decay? That "patina" of biofilm?

It's okay.

It's normal.

Their presence "waxes and wanes" to a certain extent- the product of a botanical bioload. Yet they're always there, as they are in natural habitats. And making the effort to understand and even appreciate their appearance as a sign that your aquarium is functioning as Nature intended is the biggest step in achieving what can only be called a form of "aquatic enlightenment." 

The accumulation of materials- dissolved substrate constituents, decomposing leaves and botanicals, bits of biofilms and fungal threads- is fundamental to the ecology of our aquariums.

It's part of this type of approach. It's present in all natural aquatic systems. We just work with it instead of against it. Instead of trying to sanitize, edit, or otherwise "redirect" Nature, we understand that it will follow its own path, sometimes going through phases that we may not appreciate.


And guess what? It never stops.

You wouldn't want it to.

The ebb and flow of life in a natural, botanical-style aquarium is much like a garden. You can and should perform regular maintenance, conducting water exchanges, filter media replacement, etc.- like you do in any other tank. However, you need to conduct these maintenance sessions not with the idea of "THIS will take care of those biofilms", but an attitude of. "This will continue to facilitate change over time..."

Yeah, it requires a certain attitude.

And a willingness to look at Nature as she actually is- and to appreciate the beauty in the details of her processes.

So, on a practical, functional level, is there an issue in allowing these materials to accumulate?

It's not like we've had no prior understanding of, or experience with this stuff in the hobby. 

One word I remember seeing in many of my dad's old aquairum hobby books that  I grew up reading was "mulm." It was a funny word. A sort of charming 1950's-60's-style catch-all expression for "stuff" that accumulates at the bottom of an aquarium.

It was- is- quite appropriate and descriptive!

To me, "mulm" is the freshwater equivalent of "detritus", which is used in the saltwater hobby extensively to describe the solid material that accumulates at the bottom of an aquarium as the end product of biological filtration.

"Mulm", however, is a bit more. It's not primarily fish poop and uneaten food.

I think mulm is also that matrix of stringy algae, biofilms, and fine particles of "stuff" that tends to accumulate here and there in healthy aquariums, What's cool about this stuff is that, not only do you see it in aquariums- you see it extensively in natural ecosystems, such as Amazonian streams.

Again, in the case of a botanical-style aquarium, "mulm" is also the broken-down leaves and botanicals. It's a part of a process that we've often called "substrate enrichment" in our aquariums. As botanicals break down- just like in Nature, they create a diverse matrix of partially decomposing plant materials, pieces of bark, bits of  algae, and some strings of biofilm.

Biological "fuel" for a functional miniature ecosystem.

In years past, hobbyists who favored "sterile-looking" aquaria would have been horrified to see this stuff accumulating on the bottom, or among the wood. Upon discovering it in our tanks, it would have taken nanoseconds to lunge for the siphon hose to get this stuff out ASAP! In our case, we embrace this stuff for what it is: A rich, diverse, and beneficial part of our microcosm. 

I encourage it to accumulate in every botanical-style aquarium I maintain.

It's an accumulation of materials which, based on my experience and that of many others, and in the presence of overall good husbandry, will not have any detrimental impacts on your aquarium and the health of its inhabitants.

You may not be convinced about this being a good thing. I get it. So, I encourage you to verify on your own.

Check your water parameters. Are you seeing surging nitrate or phosphate  levels? Lots of nasty algae? Do you have any detectible ammonia or nitrite? Are the fishes healthy, relaxed, and active? If the answer to the first three questions is "no", and the last is "yes"- then perhaps it's time to simply enjoy what's happening in your aquarium!

To accept and understand that the aesthetic of a heavily botanical-influenced system is simply different than what we've come to perceive as "acceptable" in the general aquarium sense.

Of course, the aquarium is a microcosm of Nature, and not an open system. However, in principle, many of the factors which control Nature control our aquariums, too.

Some are a bit different in "execution", but the influence is similar. 

So, apparently we have a real hobby addiction to siphoning. 

Personally, I don't do a lot of siphoning of "detritus" from my substrates, which are typically a mish-mash of leaves, twigs, and bits and pieces of botanicals. Sure, you CAN stir up this layer, and simply "swish" a fine meshed net around in the water column, and try to remove anything you find offensive.

I wouldn't get too carried away with it. 

Remember, most of this "stuff" or "mulm"-the detritus and such- is utilized by organisms throughout the food chain in your tank...and as such, is a "fuel" for the biological processes we are so interested in. No sense disrupting them, right?

What goes down...doesn't always have to come up.

Accumulation, in this instance, is not a bad thing.

Take care of your tank by taking care of the enormous microcosm within it, which supports its form and function. 

Recognizing that there is a continuous accumulation of life forms and their "work" going on in our tanks, and that we don't need to attempt to thwart it in any way, is an absolutely fundamental thing that we do. It's something that we need to accept...and enjoy.

Yes, enjoy.

No one said the hobby is easy, but it’s not difficult, either- as long as you have a basic understanding of the environmental processes and conditions within your aquarium. And the idea of leaving essential biological components of your aquarium more-or-less "intact"-allowing an accumulation of biological material- for an indefinite period of time is really compelling.

What would happen?

Stay thoughtful. Stay inspired. Stay motivated. Stay observant. Stay creative. Stay undaunted...

And Stay Wet.


Scott Fellman


Scott Fellman
Scott Fellman


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