For the love of detritus?

I've received a number of questions, and participated in a few fishy discussions lately about the benefits and pitfall of utilizing mechanical filtration media in our aquariums. Seems as thought the concept about "stuff" accumulating in our aquariums and somehow negatively affecting the environment is something we keep focusing on. Husbandry is a big, important part of fish keeping. However, thinking through the "whys? and hows?" of our husbandry practices is just as important to contemplate.

I have always been a big fan of mechanical filtration media in my tanks. Filter pads, socks, etc. In my many years as a hobbyists, I've always found them useful to remove all sorts of "stuff" from the water, and it was never a real problem using them, because I was/am obsessive about cleaning and replacing them before they become saturated with detritus and such, which break down and potentially affect water quality.

Wait a I allow that much volatile "stuff" to accumulate in my tank to the point where it gets picked up by mechanical filtration media in the first place? DO YOU?

Likely not. Nope. Not really...But I get the argument...

Now, in the reef aquarium world, a lot of people freak out about "detritus" and such accumulating in the aquarium, and they blame filter socks and media for all sorts of problems in their aquariums. I understand this concern for water quality, but I think it sort of places emphasis on the wrong part of the equation; that is, what exactly is accumulating, and why? Uneaten food? Bad! Need to be more careful here. Fish waste? Unavoidable to some extent (unless you lower population density/food inputs). You get the idea...

I think it's all relative, though. 

In a botanical-style blackwater aquarium, we tend to see a fair amount of fine "bits and pieces" of decomposing leaves and botanicals accumulate in our mechanical filter media. Funny thing to me is that this stuff, although somewhat unsightly if allowed to accumulate in the aquarium, seldom is seen doing such. And, it's just sort of "there", if you know what I mean. And, other than potentially being visually distracting, this material is not really detrimental- I mean, you want it in your system (at least in its "original" form).  It's what imparts the tannins, humic substances, and other desirable compounds into our water.

Of course, accumulations of uneaten food, fish waste, etc. is just as undesirable, right?

Well, let's revisit the "aquarium definition" of detritus one more time:

"detritus is dead particulate organic matter. It typically includes the bodies or fragments of dead organisms, as well as fecal material. Detritus is typically colonized by communities of microorganisms which act to decompose or remineralize the material." (Source: The Aquarium Wiki)

And back to the reef world again for a minute. 

I know a lot of reef hobbyists who are making the decision to yank their mechanical filter media (pads or filter "socks") out, and either forgoing them altogether, or utilizing materials like foam sponge, which is much easier to clean than those filter socks and polyester pads. The thinking with the people who have yanked the materials altogether is that they feel that the longer material is in circulation within the aquarium, the more likely it is that someone might consume it. Logical. In a reef tank, with all sorts of mouths and tentacles and other feeding appendages, this has a definite grain of truth to it; perhaps a little less so in the freshwater tank, IMHO, although those of you who are experimenting with "inoculating" your botanical beds with creatures like worms and aquatic crustaceans will definitely have some very interesting results to draw upon!

On the other hand, if most of what is accumulating in your mechanical media is just broken up bits of botanicals, I'd have little concern. If it's uneaten food, on the other hand, you need to figure out a more accurate feeding approach. "Detritus" in general, in my opinion, gets a kind of a bad rap, as the bulk of it is really broken down already by the time it accumulates. And there is a certain argument that some amount of this material, if allowed to settle in the aquarium, becomes a basis for biofilms/fungal growth- part of the "food web" in our tanks. 

And I wonder how much of this stuff is really accumulating in a well-managed, under-populated, and carefully-maintained aquarium? Sure, in systems with large, predatory cichlids and messy eaters, you're likely to see a lot more than you would in a lightly-stocked tank with say, Endler's Livebearers or Gouramis, but most of us really overfeed THAT much? I don't think so. Of course, if you see uneaten food and such accumulating in your tank, it looks crappy. However, do you have phosphate or nitrate issues as a result of accumulating organics from this stuff, or is some of it- enough of it- being utilized by bacteria and other "unseen residents" of your tank that it's not really a "problem" from an environmental standpoint?  What does the test kit say? 


I can't help but wonder if our aversion to seeing any amount this stuff in our tanks is much like the aversion many have had to blackwater tanks: It LOOKS "dirty" because of the color, so it must be "unhealthy" or otherwise "bad."

We've become militant about this "pristine-looking" aesthetic. Take a snorkel in an Igarape next time your in The Amazon and you might re-think your definition of "pristine."

Think about it from that perspective for a bit.

And I also wonder, in a tank where we are purposely cultivating small crustaceans and worms and such, will many of these creatures get stuck in very fine mechanical filtration media? Perhaps the coarse sponge is better? I mean, if you're trying to cultivate food, it makes no sense to have 40% of it or whatever end up in your filter media, right? I've offered this thought before and I'll mention it again: Perhaps we're a bit too obsessive about removing "everything" from our water?

This is an age-old aquarium management issue, that goes back and forth trying to strike a balance between "too much" and "too little" of feeding versus filtration, isn't it?  And when you throw aquatic plants into the equation, could they be utilizing some of the extra dissolved organic carbons or other nutrients found in some of this detritus for their growth? I mean, it really is about balance.

Regular water exchanges are a great way to keep this balance, as you've no doubt have had beaten into your head since your aquarium-keeping "infancy."

So...we're back to the beginning, yet again.

Ahh, "detritus"- menace or benefit? Or perhaps, something in between? Like biofilms, fungal growth, aufwuchs, and decomposition- is it something that is inevitable, natural- perhaps even beneficial in our aquariums? Or, is it something that we should learn to embrace and appreciate? All part of a natural process and yes- aesthetic- that we have to understand to appreciate?

We've touched on this topic before, but fellow hobbyists keep asking me my thoughts, and they have evolved over the years. I think so many things in moderation are pretty good- even things that we have historically "freaked out" about. Yes, hardly a staid, scientific conclusion, but I think valuable from an aquarium management perspective. Moderation.

What do you think?

Stay calm.

Stay thoughtful.

Stay observant.

And Stay Wet.


Scott Fellman

Tannin Aquatics





Scott Fellman
Scott Fellman


1 Response


May 26, 2017

That last photo of the detritus-covered branches is what really inspired me to go hard with a “dirty” blackwater tank, and I’m loving it thus far. “Filthy-looking” doesn’t mean “careless” or “low-maintenance”!

Now, in nature, there is a greater volume of water to dilute the amount of nasty stuff that happens, but we can easily accommodate that by choosing to understock our aquariums, and also by doing regular water changes – I do 10% weekly in my understocked 35, and 25% in my at-capacity 20. Two months in, I have yet to vacuum the substrate, choosing instead to allow the “cleanup crew” (infusoria, microworms and “pest” snails) to break down the waste, while providing a foraging food source for my loaches. Integrating plants helps a lot with processing the nitrogenous compounds, and there is a plant for almost every freshwater/brackish situation, no matter how tinted. Even the algae fuzz that occasionally blossoms from my aquatic botanicals helps reduce waste while providing a natural food source.

I’m interested in the removal of the mechanical filtration process. I have a prefilter sponge for keeping the kuhlis and shrimplets safe, and keeping the coconut fiber that they kick up while foraging out of the impeller. I have often wondered if just removing the internal sponge and loading my HOB with Biomax pellets or similar would provide the beneficial bacteria filtration that I need, while the microfauna consume the rest of the waste.

I think that freshwater ecosystems can be capable of everything that a saltwater system can, I just think that we need to find new approaches that break the mold of traditional fishkeeping – and I think that botanical tanks are the method in which this transformation of thought and practice will take place. It’s a bold experiment, not without risks, but perhaps worth trying – cautiously.

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