Can you dig this?


There are certain "truisms" and "rules" in aquarium keeping that have been around for decades.

Many of them make a lot of sense, and are based on the experience of millions of aquarium hobbyists over a century of aquarium keeping. Others are newer, and have proliferated more recently online and elsewhere. Some have become distorted, distilled, and otherwise "altered" over time, becoming a mixture of hard facts, partial information, assertions, and assumptions.

Today's piece is about just such a topic; one which I kind of need your help on. I've taken a lot of this at "face value" over the years, but recently, I've kind of given it more thought and wondered if what we've been indoctrinated to follow without question for a century might just have been misinterpreted or incorrectly been given an excess of credence for perhaps the wrong reasons?

Here goes:

We hear a lot in aquarium keeping about the need to keep our substrate level undisturbed as much as possible. And I know it makes sense to some extent, right? The deeper laceless of the substrate is where a tremendous amount of biological activity- dentrification, specifically- occurs. And the conventional aquarium theory is that disturbing the deeper layers of substrate creates a mixing of materials and disrupts the identification process by releasing gasses and "aerating" the anaerobic regions of the substrate or something, right?  Or is it something else?

What exactly is the rationale here? I mean, physically moving around substrate layers through vacuuming of fish activity or what not isn't going to "knock all of the bacteria off of the substrate material", right? And then they're just going to be pissed off and stop consuming organics?  I mean, seriously? Don't filters contain much- if not more- of the same bacteria, probably doing the lion's share of the work, as water is continuously flowed through them? And I know hundreds of hobbyists who maintain bare-bottom reef and freshwater aquariums without issues.

Let's be honest, I am of the school that says "By all mean, disturb your substrate...within reason!" Like, often. I mean, you get buildup of organics debris, fish waste, uneaten food (gulp)...If you doubt this, move a rock or piece of wood in your tank that hasn't been disturbed in a while, and see all of the stuff that comes up- even in a "clean" tank. I believe that you should remove excess accumulations of "stuff" (how's THAT for being technical?), while doing your best not to decimate any interstitial organisms (worms, snails, etc.) that might be dwelling within the substrate. It's okay to leave "some" material in there. It feeds beneficial bacteria and "those creatures" who reside there...

Besides, in nature, the upper layers of substrate are continuously being disturbed by water movement, fishes, etc. Some fishes, like Geos, etc. spend a large part of their day sifting for food in the substrate. Do their aquariums "crash" or suffer chronically from disturbing the sand bed? I submit that they don't, because most hobbyists who keep messy fish like this employ other methods (like great filtration and water changes) to mitigate the disturbance being done by the fish's digging activities.

And the reality is that there is a lot of macro/micro life in the sand beds-in both aquariums and in nature, and these organisms need food. So, although you don't want to go crazy, it's okay for some stuff to accumulate in a substrate bed, IMHO. The idea is to get a decent amount of substrate movement and disturbance at the top layers, to help keep gross particulate from accumulating, while at the same time letting some material in there to feed the organisms which reside in the substrate. The best of both worlds, right? Moderation.

Is it? 

I think so. 

Is this yet another case that's analogous to the kind of baseless fear many hobbyists had about blackwater tanks for so long ("If the water is dark, it MUST be dirty, right?"), or is there a genuine reason we should be afraid to disturb our aquarium substrate?

Now, I CAN See a few cases where you wouldn't want to disturb the substrate. Planted aquariums should typically not have the substrate disturbed because the roots of the planet will be affected. Makes perfect sense. And, if you're using materials like dirt with a "cap" of snd or gravel, you'd simply make a mess of your tank by intruding into the substrate. A reefer with a well-stocked sand bed (i.e. one with lots of interstitial life, such as various worms and crustaceans) has different reasons for not wanting to disturb the substrate. Makes sense- you're uprooting and disrupting your little friends' world down there. 


And, with our increased experimentation into "botanical bottoms", what's going on in the substrate is definitely something we should be interested in, IMHO. Now, granted, ours is a world of actively-decaying materials, perhaps loosely aggregated, generally on top of a more traditional sand or gravel bed...yet some of the processes occurring within deep layers of botanical materials might be similar to what happens in sand or traditional substrates, right? A lot to research.

Some reefers go the other way, and would have you believe that you're going to realize all sorts of bad stuff, like phosphate and nitrate, even sulfur dioxide storms, will be unleashed if you disturb the sand bed. Now, I agree, you can release a lot of debris that can cloud your tank if you stir way into a deep sanded. And there is not doubt some organic phosphate and such bound up in some of this gross or fine particulate matter, which will be released into the water column...However, is there a documented scientific rationale for not ever disturbing anything but the very top layers of substrate?

And is your tank so poorly maintained- so "balanced on a razor's edge", that a stirring of the substrate will unleash armageddon? Hmm, if so, I think you need to re-think your general husbandry approach a bit.  And I'm not suggesting that there are no consequences to disturbing a deep sand bed...I'm just wondering what they might be in an otherwise well-maitnaiend aquarium. DO we know, or are we making some sort of assumptions, or...?

I'm not trying to launch some kind of all-out assault on one of the basic tenants of aquarium husbandry. I'm simply asking for some clarification. And, quite honestly, it's not all that clear...if you look up this topic online, "answers" are all over the map. We have hobbyists from both camps (disturb/DND) stating their positions, but there seems to be not a ton of great confidence-building facts (outside of the ones I mentioned) for the "DND" crowd to bring forward.

I think there are a lot of good points on both sides, but I'm concerned that the overly-generalized, excessively dogmatic, heavily-regurgitated rationales for either belief render this another one of those topics which we need to "pick a side" and experiment for ourselves. By bringing these types of topics into a more active discussion from time to time, and asking for more specific clarifications, I think we actually do the hobby a great service.

So, without stirring up (couldn't resist) further controversy on this topic, let's hear your thoughts on the subject.


Stay inquisitive. Stay logical. Stay thoughtful. Stay creative.

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses


May 29, 2017

I’ve got cories and plecos that are constantly re-scaping the tank with their digging, and I’ve had no problems at all (save some Columnaris from Petsmart fish, I know, dumb move)


May 29, 2017

I’m sure that I’ve said it before, but I’ll say it again – in dozens if not hundreds of hours of painstaking research on freshwater deep sand beds, dirted tanks, Walstad-type tanks and more, I’ve only encountered TWO confirmed, firsthand cases in which disturbing the substrate wiped out a tank, and they were both aquariums that had left their substrate undisturbed and unmaintained for YEARS – 5 and 10 respectively. Substrate maintenance is easy and important – in the wild there would be invertebrates, amphibians, plant roots etc. digging around in there, constantly turning things over. At minimum, take a stick and poke around a bit in the substrate before your weekly water change to release any small bubbles that might have built up.

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