The (gooey, slimy, and weird-looking) cycle of life in our aquariums...


So, I was thinking about this the other day:

Ever noticed how an aquarium is so much like the natural world in many ways?

I mean, sure, it's a closed ecosystem in a box, but it goes through so many of the processes which occur in natural waters of the world. Innundation, transport of new materials into the ecosystem, recruitment of life forms, etc.

Fishes live out their lives, eat, reproduce, die in the system. Sometimes, we can't find the bodies of the fishes...and it sounds gross, but nature never wastes anything, does it? Their bodies fuel fungal and bacterial growth, and while decidedly horrifying to us, this process simply contributes to the overall function and "richness" of the environment.

Okay, that's gross, but conceptually...right?

Decomposing botanicals can certainly be viewed in some sense as "bioload" on the system, in that they foster bacterial and fungal action to break them down, and that these life forms respire, produce waste, etc. However, they also contribute to the food chain in our tanks, don't they?


And there's always that biofilm. 


Even the word conjures up an image of something that you really don't want in your tank. Something dirty, yucky...potentially detrimental to your aquarium's health. 

And, let's be honest with ourselves here. The damn dictionary definition is not gonna win over many "haters":

bi·o·film -ˈbīōˌfilmnoun -a thin, slimy film of bacteria that adheres to a surface.
Some charming and commonly-encountered examples of biofilm include plaque that forms on teeth, and the slime that forms on surfaces in water.
Shit. Really?
Yeah, I guess that's the definition we have to run with.

Well, apart from the unpleasant-sounding description of the stuff, the concept of biofilms and how they form is actually kind of interesting. Not "charming." I didn't say that. But interesting for sure.

Biofilms form when bacteria adhere to surfaces in some form of watery environment and begin to excrete a slimy, gluelike substance, consisting of sugars and other substances, that can stick to all kinds of materials, such as- well- in our case, botanicals.

It starts with a few bacteria, taking advantage of the abundant and comfy surface area that leaves, seed pods, and even driftwood offer. The "early adapters" put out the "welcome mat" for other bacteria by providing more diverse adhesion sites, such as a matrix of sugars that holds the biofilm together. Since some bacteria species are incapable of attaching to a surface on their own, they often anchor themselves to the matrix or directly to their friends who arrived at the party first.

Sorta sounds like Facebook, huh?

(The above graphic from a scholarly article illustrates just how these guys roll.)

And we could go on and on all day telling you that this is a completely natural occurrence; bacteria and other microorganisms taking advantage of a perfect substrate upon which to grow and reproduce, just like in the wild. Freshly added botanicals offer a "mother load"of organic material for these biofilms to propagate, and that's occasionally what happens - just like in nature.  

Yet it does, so we will! :)

Is there a "darkside" to biofilms?

Well, of course.

Like anything else, too much of a "good thing" can cause problems in rare instances. Frightening, "aquarium armageddon scenarios" could play out. For example, in an extremely overcrowded aquarium (or a very small one) with marginal husbandry and filtration, with a huge amount of biofilm (relative to tank volume) caused by an equally huge influx of freshly-added botanicals, there is always the possibility that bacteria within the biofilms can multiply extremely rapidly, reducing the level of oxygen in the rest of the aquarium, which could lead to a dramatic reduction of CO2 being released out of the water. This, in turn, could lead to CO2 levels rising quickly and sharply, potentially causing asphyxiation to the animals in the tank- including the lovable nitrifying bacteria that support it.

Now, that's a true "doomsday scenario"- brought about by a non-sustainably-managed/populated aquarium, improper preparation and rapid, excessive additions of botanicals, and complete lack of common sense on the part of the aquarist, in terms of husbandry.

So yeah. There IS a darkside to biofilms.

If you create circumstances to foster one.

The real positive takeaway here: Biofilms are really a sign that things are working right in your aquarium! A visual indicator that natural processes are at work.

Yet, understandably, it may not make some of you feel good.

First off, take comfort in the fact that this is typically sort of a passing phase, and can take anywhere from a few days to 2-3 weeks before it subsides on it's own to some level that you can live with. Realize that biofilms are present in every aquarium, to some degree.

Yeah, even your "Nature Aquarium", guys.

Welcome to Planet Earth.

And have you ever noticed that the longer you let a tank run...especially in a blackwater, botanical-style tank- it sort of settles down, and gets through these seemingly endless periods of cloudy water, biofilms, generally "dankness" (as one of my hipster fish-geek friends calls it)- and then just sort of "arrives?"

It happens. All the time.

You need to harden yourself to the seemingly unsettling, "dirty", and "funky-looking" phases that your blackwater/brackish, botanical-style aquarium will go through as it "runs in", establishes itself, and evolves. 

It's "par for the course", and if you freak out, jump ship, bail out- whatever you want to call it- during the critical early (and admittedly often less aesthetically pleasing) phases of your tank's evolution, you miss out of so many amazing things.

Stay the course. Don't be afraid. Open your mind. Study what is happening. Draw parallels to the natural aquatic ecosystems of the world. Look at this "evolution" process with wonder, awe, and courage. And know that the pile of decomposing goo that you're looking at now is just a steppingstone on the journey to an aquarium which embrace nature in every conceivable way.

Stay brave. Stay thoughtful. Stay enthusiastic. Stay open-minded. Stay engrossed...

Stay with it...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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