It's the one thing....

The aquarium hobby is pretty weird, when you look at it from an outsider's perspective...I mean, be honest- it really sort of is. That's not at all a bad thing...just a fact! We're into some pretty obscure stuff. We have become "experts" on some real minutiae about fishes...and that's pretty cool, if you look at it objectively!

We talk a lot about some pretty arcane subjects in this very blog- and in this hobby, don’t we? Part of this is because most aquarists are as complex as their aquariums…endlessly diverse, and generally quite interesting (okay, there are likely a few fish geeks who are just..dull. Hey, I’d be full-on lying if I said otherwise, right?). There are many different paths to success with aquariums, of course; however, I think that there us actually ONE key thing that your aquarium needs to be successful.

Yeah, you heard me. ONE KEY THING! 

That’s a rather strongly assertive claim, coming from me,Mr.-Don’t-Take-Anyone’s-Advice-Too-Seriously himself, huh?

Okay, I’ll own it. I really do think I know the ONE thing that every aquarium needs to be successful.

Not fancy low-iron glass tanks, electronic controllers, state-of-the-art filters, Mars Rover-style plumbing scheme, multi-chip LED lighting systems. All nice things to have, of course...However, you need NONE of that to be successful.

The one thing that an aquarium needs to be successful is stability.


Yeah, that's what every aquarium needs to be successful.

Think about it for just a second, as you contemplate beating the shit out of me for a very gross over-generalization- something I’ve admonished everyone in the hobby never to do. Yeah, stay with me for a sec, okay?

The majority of the wild aquatic habitats we love to emulate are among Nature’s most stable environments. Sure, some are subject to seasonal fluctuations, impacts of weather, and more recently, mankind's influence and such, but for the most part, "in any given season", the conditions remain rather predictable.

However, as I just mentioned, they’re constantly under siege from external forces, aren’t they? We read about the impact of global warming, pollution, deforestation, increasing acidity in the oceans, pollution, over-fishing, etc. What do all of those factors affect? Stability. Why are these factors so impactful and potentially dangerous?

Because they threaten the stability of these fragile ecosystems.

Sure, we can make some rather blanket statements based on our 100-some years of experience with the aquarium-keeping hobby that most fishes are really adaptable, hardy animals, coping with the rigors of collection, transport, acclimation, imposed propagation, etc., and still apparently thriving. True, many fishes are more resilient than you’d initially believe, coming as they do from such seldom-changing environments.

However, just because your wild Geophagus, Discus, characin, or Betta manages to hang on for a while in sub-par environmental conditions during transport, at the wholesaler  and ultimately to you, does that mean it’s “adaptable?" Well, maybe. However, I think it might be more accurate to state that it simply tenacious- clinging to life in environmental conditions that are otherwise less-than acceptable to it?

I think so, in any case.

Does this mean it’s okay to provide an environment that is less than very stable?

I don’t believe so.

Now, I know what you’re probably thinking: “Here’s Fellman, spouting off about stability on one hand, and then telling us not to obsess over chasing numbers with our water chemistry…And he’s pushing botanicals as a means to attempt the replication of highly specialized aquatic habitats with no real point of reference. What gives here?”

(Okay, maybe you weren’t thinking of all THAT, but I’ll bet you were thinking about why I am such a big fan of stability, right?)

Fair question. Perhaps I can create a sort of analogy that makes sense (maybe- you know my analogies can go south quickly)…

Let’s say, for example, that you’re in captivity (just the SOUND of that sucks, huh?), plucked off the street by a human collector. You’re kept in a comfortably furnished apartment, with some plants, pizza, a nice couch, fast wifi, and all the Instagram and Netflix you can handle. That’s sort of your new life. You’re confined to these four walls, day in and day out.

Almost as soon as you arrive, the careful conditions that were arranged for you will start to deteriorate. The air gets a bit stale, some crumbs and such are accumulating on the floor (I don’t care how careful you are- you’ll leave crumbs when you eat pizza…), the bathrooms start getting a bit dirty, light bulbs start losing brightness; you’re sick of watching reruns of “Pacific Rim” and "Game of Thrones” on TV (I mean, I would be.)

Within a few weeks, the apartment is a serious college dorm-room-style mess. It needs a good cleaning. Oh, and you can’t leave. Ever. Fortunately, the housekeeper arrives. The bathrooms are cleaned., floors vacuumed, furniture refreshed, and linens changed. You can breathe again. Fast forward two weeks. Same situation. The place is a mess and you’re getting bit crazed from the clutter. Oh, and did I forget to mention, you can’t ever leave? Oh, the housekeeper is on vacation. Can't come on's gonna be another two weeks or so.

The housekeeper comes, eventually. Your apartment is clean again...for now.

And so on. Sure, it seems okay from a “comfort provided” standpoint, but the reality is that you’re constantly forced to stay in the same place, and it keeps changing- swinging back and forth between extremely dirty, and otherwise tolerable. And, did I mention, you can never leave?

Yeah, I did.

What does all of this mean to you, the resident?

You’re constantly having to adapt and deal with stress. Stress from a myriad of factors, ranging from the same food, sounds, four walls, to a dirty-then-clean-then-dirty environment. This seems innocuous at first, but the constant adaptation to changing conditions in a closed environment is quite stressful.

Fishes, hailing from some of the most stable environments on the planet, are simply not evolved to handle the stresses cause by constant environmental fluctuations without incurring some health issues as a result. When you factor in temperature swings, increasing/decreasing alkalinity and pH, trace element levels, etc., it’s a recipe for stress, plain and simple.

And, I believe that stress is a problem for fishes- particularly, stress brought about by constant environmental fluctuations.

Sure, it seems painfully obvious that we need to keep environmental parameters stable for our fishes. I don't think anyone makes it a point to create wild environmental swings in your aquariums. However, "shit happens" and we sometimes have to postpone water exchanges, routine maintenance, etc. And, like I discussed above, fishes are reasonably rugged, tolerating periodic environmental variations. But wild parameter swings? Not good. 

Now look, I’m not telling you to lock in on set numbers at the exclusion of everything else. I’m not telling you that a 2 degree day/night temperature change is going to be the demise of your tank. What I am suggesting here is that you look into the overall environmental stability that you are providing your animals. This includes things like feeding, use of additives, changing fertilizers, etc. When you mix up environmental parameters, or are sporadic in husbandry, in my opinion, you’re forcing fishes to adapt to constant changes that they are likely not evolved to do.

Rather than obsessing on, for example, a phosphate level of exactly 0.5 ppm, you can lock in on a range within the target parameter of say, 0.5- 2 ppm or whatever, and avoid rapid, wild deviations on either end. I know from experience in reef keeping that raising or lowering parameters like magnesium, for example, by more than say, some very small percentage likely creates potentially stressful conditions for your corals. Now, fishes aren't quite as touchy as corals, but the idea here us the same. Constantly forcing your animals to adopt to changing environmental parameters- regardless of reason- is problematic.

Stability in a range is also about consistency.

Consistency in husbandry practices, frequency of water exchanges, filter media replacements, brand of salt mixes (in a reef tank), feeding, photoperiod, etc. is the name of the game, IMHO. We often hear about the hobbyist who never seems to follow the age-old practice of regular water changes, changing filter pads, etc., yet has had an amazing tank, or tanks for years. We’re quick to point out that he/she is just being “lucky”, and that the error of his/her ways will catch up at some point. And it never seems to, have you noticed that? Oh, I suspect that at some point, lax maintenance practices will catch up with you, but I also think that the fact that the environment in the subject tank is consistent (on whatever side of the range that it’s in), a variable is eliminated (environmental fluctuation).

And THAT may be the reason for the apparent "success" of an otherwise “contrarian” aquarium system. Although parameters may not be optimal for long term growth and health of the fishes, with increasing nitrate and other organics likely not being fully metabolized and utilized by the life forms within the system, they are not constantly shifting, either, -just building. Meaning that the “lesser of two evils” in this case may just be fluctuation, rather than parameters that don’t “meet the gold standard” of generally agreed-upon aquarium keeping practice.

Strange, but it makes sense in my mind!

And, I suppose that one can even make a somewhat convincing argument that even regular water changes are a stress-infusing event for fishes or aquatic plants, forcing them to endure “resets” or changing parameters as a result of the change!

Bizarre, huh? And where does this leave us as aquarists? What’s the best course of action? I mean, I've quoted the words of a child before- "Fishes don't break that easily." 


Within reason, of course.

The occasional wild change may be stressful, but most fishes can "pull through." However, constantly having to adapt to wildly fluctuating environmental parameters is just pure stress for aquatic animals.

That's why I always encourage newcomers to our world to move very slowly when adding botanical materials to an established aquarium. Even casually manipulating many environmental parameters in an aquarium can create potentially stressful situations for fishes. This problem is exacerbated by “casually” adding a “little bit of this and a little bit of that just because”, as has been customary in a lot of reef aquariums in recent years. In the reef world, you'll see hobbyists lose their minds searching for the perfect tank, adding a little of this or more of that in some quest for something...

The short and sweet guide to adding "stuff" to tanks? If you’re going to add some chemical addictive to your aquarium, or attempt to remove something, make sure that testing dictates that it’s necessary. In today’s high-tech information-enabled aquarium world, there is no need to guess about stuff like this. The data is there for the taking. Make changes based on your system’s actual needs, not supposition!

Now, with our botanical-style,blackwater aquariums, we ARE sort of contradicting what I'm saying, just a bit, I think.  

We toss in all of these botanicals without knowing exactly how a given additional influx can influence basic water parameters...It's as much of an art as it is a science...So I selfishly and shamelesslly give us a "pass" for now...but only during this "experimental phase", okay? We'll eventually have to get a bit more methodical, IMHO.  Maybe eventually we'll have more reliable testing for specific tannins and humic substances, etc. imparted by various botanicals.

Eventually, one can hope!

The limiting factor in our world is being able to ascertain the influence of everything we add. We are not able to test, or example, tannins (well, there ARE kits to test for them, but they express as ppm or some other measure that really doesn't much reference point for us as fish geeks...and there are hundreds of types of tannins, so...yeah). We talk about adding "x" number of leaves in a given sized tank...well, some of us do. (I fear doing that, lol.)

Perhaps, however, testing for contractions of some of these things in wild habitats will ultimately provide a very rough "baseline" reference?

As far as aquarium testing- We're limited to pH, alkalinity, TDS, conductivity (redox), and the usual suspects (nitrate, phosphate, etc.). We need to focus on a few basic parameters, like pH, alkalinity, and TDS when managing these tanks, IMHO. Nitrate and phosphate are also useful. We can still keep things "stable within a range" in this type of system- and we should. And we can know, for example, when "enough is enough" for our tanks. We can ascertain when we are pushing it too hard, too fast...and we can still moderate our big moves with discipline and the embracing of this philosophy of seeking stability.

Reducing variables and creating stability is a great overall aquarium husbandry practice, because it plays right into the evolved need of aquatic life forms favoring a consistent set of environmental parameters.

I therefore submit that environmental stability within a range is the single most important thing that your aquarium needs in order to be successful is consistency. So it’s not just about using the same source water, plant fertilizers, botanicals, salt mix, etc…It’s also about doing the same things repetitively- things that reduce environmental variables and inconsistencies that can negatively impact your fishes, plants, and corals.

Developing-and maintaining-good, regular habits.

We should spend at least as much time plotting out how to keep our aquariums stable as we do deciding which LED lighting system to purchase. Indeed, factors such as how to provide stability should INFLUENCE our purchase decisions!

So, in summary- whatever methodology and course of care you choose to provide your aquariums-  be sure to do it with purpose, thoughtfulness, and consistency. What are a few things you can do as a hobbyist to promote consistency in your system? Here are five that come to mind right away; I’m sure you’ll have more:

*Acquire the largest aquarium that you can comfortably manage. Larger water capacity provides greater stability and environmental consistency. Besides, what a rad excuse to purchase a larger tank, right? 😆

*Use the same products (ie; salt mixes, essential additives, etc.) regularly- if you use such products to begin with. Alternatively, use the same source water for all water exchanges...

*Engage in the same husbandry protocols regularly (ie; water changes/no water changes 😂, media replacement, feeding, etc.)

*Target ranges for water chemistry parameters that are easily achievable and maintainable, with any adjustments made solely as dictated by testing.

*Observe your system carefully and often to assure that conditions are not deteriorating. Establish routines for a variety of aquarium-related tasks.

In the end, aquarium-keeping is really all about creating a controlled environment for animals that are utterly dependent on us- and managing a hobby that is enjoyable and not burdensome. Keeping live animals in captivity IS a responsibility, but it need not become a chore.

In the end, it is supposed to be about fun, right?

It's about observation, interpretation, nuance, and finesse...And repetition, too! Doing the same things that work on a consistent basis. However, don't go crazy in this pursuit of consistency...Just relax into it and think about the impacts of everything you do with your aquariums...

Encourage stability.

Until next time, keep things consistent, but be sure to keep the “fun level” up…

Keep learning. Keep sharing. Keep growing.

Stay diligent. Stay observant. Stay thoughtful. Stay flexible...

And Stay Wet.

Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

September 14, 2019

Hey Florian!

Yeah, the pizza part of the equation was pretty good, actually!

Good question on water exchanges. In my opinion, a blackwater aquariums should be managed just like any other. The water exchanges can be at a percentage you are comfortable with. I personally have always been a 10-20 percent weekly water exchange guy. I don’t see any issues with regular water exchanges in blackwater tanks at all. Again, to me it’s about consistency. And that goes for the water that you’re using for the exchange, right? I tend to have a supply of “pre-tinted” (or more correctly stated- conditioned) water of the same pH/alkalinity characteristics of my aquarium, and do that.

Quite frankly, I sometimes wonder about the necessity for greater water exchanges in blackwater tanks…I mean, we DO keep a lot of botanical materials n there- which decompose of course, and have SOME impact on water quality…Although a properly stocked system with a mature biological filtration regimen should be able to break down most of the accumulated organics, right? And if you have plants, it’s another “plus” on your side! Of course, the water exchange serves many purposes, besides just dilution of nutrients, but all in all, I am of the opinion that a well-managed blackwater, botanical-style aquarium places no greater water exchange requirement on the aquarist than any other type of aquarium. Granted, observation is key…as are common sense overall husbandry practices. I think you’re doing it right! No two tanks are exactly alike, so rather than recommendation of a specific amount of water being exchanged, I’m more about…you guessed it…consistency. Change the same amount of water at the same interval in the same way…

Hope this stimulates more thought! Something we could (and should) discuss more sand more in the future!




September 13, 2019

Hi Scott,
the comparison you made doesn’t really work for me … my appartment does undergo pretty much the “fluctuations” you described. But I’m not a fish, we don’t know how they “feel” or probably not even what it does to them physiologically when we change decor or the pH goes from 6 to 6.5 or whatever changes we (or nature) put them through. And as far as that comparison goes, billions of people on this world would gladly take the free flat with pizza and netflix and a housekeeper ;). Anyhow, I get what you’re getting at.

This post though brought me to a very practical and mundane question: am I putting my fish through intense stress by doing too large water changes? In my blackwater tank (90 liters, rather lightly stocked) I change 1/2 of the water weekly, just because that’s what’s recommended for aquascape tanks and I do this with my heavily planted and fertilized tanks.
I’ve never questioned that much although when I had my first fish tank 25 years the recommended water change was 1/3-1/4 every two weeks.

What’s your opinion (and sorry if you’ve answered this 100 times already) on water changes in a blackwater tank? Does it need less, more, same, depends, compared to other tank styles, like your typical aquascape?

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