Celebrating the slimy stuff...a quick refresher on biofilms...

Your tank is looking awesome. The hardscape is down. The leaves and seed pods are in place...and then..it hits...


Yeah, you notice some strands of the icky-looking, yucky stuff...that gooey mess of sugar and bacteria that forms what we now accept in the blackwater/botanical-style aquarium world as a sort of "right of passage"- the point where your aquarium has exited the "biologically-sterile" phase and begins its journey towards becoming a diverse, naturally-functioning microhabitat.

We've all been there.

There is that initial "freak out" in many of our heads, which makes you doubt what your doing...has those little questions sneaking into your head. And of course, you do as we do... you dutifully scan all of those cool underwater pics and videos and come to the realization that most aquatic habitats are hardly the pristine, glossed-over aquarium "look" that we have dancing around in our minds.

And then we consider what's really happening; what it all means.

Suddenly, it begins to make sense: When we set up an aquarium in this fashion, we're supposed to expect this stuff to form. In fact, we encourage it and dare I say, celebrate it! Well, I suppose it's easy to NOT want to "celebrate" it's appearance, but it is important to understand it, rather than loathe it.

bi·o·film -ˈbīōˌfilmnoun -a thin, slimy film of bacteria that adheres to a surface.

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.

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! :)

It's one of the major components of the "mental stretch" that we as hobbyists must make when we get into using botanicals and leaves in our aquariums.

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 mentally live with. And of course, you must realize that biofilms are present in every aquarium, to some degree. Yeah, even you "Nature Aquarium", guys.

Welcome to Planet Earth.

Yet, there are always those doubts...and some are not willing to sit by and watch the "slime" take over...despite the fact that we know it's okay...

And when you've got a lot of this material in your aquarium, and it's causing you considerable worry, stress, and just plain giving you a case of the shivers, there are some actions you can take ( besides cursing the whole idea of throwing aquatic botanicals in your system in the first place).

What to do? Here are a few time-tested options:

  • You can wait it out. That's right. Do nothing, except appreciate the wonders of nature, no matter how unsightly they may be at times. I mean, didn't nature make the "Death Flower" and the "Slime Mold?" Seriously. Yeah. And this is nicer to experience than "terrestrial" biofilms, like, oh, let's say... plaque!


  • You can remove the offending botanicals, give them a good scrub with a soft bristle brush (like an old toothbrush), a rinse in fresh water, and put 'em back in.


  • You can remove the botanicals, give them a good scrub, and re-boil/soak them again. Although a bit redundant, and in our opinion, not necessary, this procedure does have the advantage of removing some of the trapped organics that lead to the initial "outbreak", but you may see it happen again.


  • You can leave the botanicals in place, and employ some natural "control", in the form of ornamental shrimp. Yeah, that's right- your "Crystal Red Shrimp", "Bee Shrimp", and the rest of those tiny, overpriced, yet engaging little crustaceans  absolutely adore biofilms, and will attack it voraciously. Alternatively, we've learned that some fishes, like Plecos, some Corydoras cats, and even Leporinus and other "Headstanders" seem to pick at this stuff fairly aggressively. In fact, I've seen Pencilfishes and other small characins pick at it.

Remember...always remember...

Biofilms are  common in nature, and a part of pretty much any aquarium, yet a bit more significant (and noticeable) when you play with aquatic botanicals. They are not to be feared- although they should be respected- and ultimately, utilized as food by your animals!

But you knew that already, right?

Stay calm. Stay determined. Stay brave. Stay devoted...

And Stay Wet.


Scott Fellman

Tannin Aquatics  

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

November 28, 2017

Wow, Pilar- plenty of possibilities…and of course, the options/prices are right here on the site. I’d start with one of our variety packs and maybe supplement with a few “a la carte” botanicals…I tend to like leaves and smaller botanicals with the little fishes- but it’s personal preference…If you need additional assistance, just reach out on our chat or Facebook forums and we can help you out!



Pilar Morgan
Pilar Morgan

November 23, 2017

The most I’ve done is throw a leaf or two in an aquarium. I usually read your articles with the mindset of one who knows she’ll never try the products because I dont know how to use them. Today I read an article on biofilm and now I’m curious. Which products would I use for a 29 gallon freshwater tank with harlequin rasboras, pygmy sparkling rasboras and celebese rainbow in it? What particular combination of products would I use and how much would it cost? Thank you.

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