The Acid Trip...

Are you experienced? 

The expression above comes from cultural history..specifically of the 1960's counter-culture, when the generation gap was obvious, "peace and love" were the antidote to war, Woodstock was "the thing", the seeds of rebellion were in the air, and acid was on a lot of people's minds...

Okay, different kind of "acid" than we're going to talk about today...but I felt the title was catchy enough! 😎

And I suppose, the kind we're into could be "mind-altering", to a certain extent...

We discuss the idea of "soft, acid water" in the context of blackwater aquariums, or , for that matter, aquariums in general over the decades. It's that half-mythical "destination" that many of us want tot achieve to create conditions for a host of fishes. Some of us are lucky enough to start out with soft tap water of negligible carbonate hardness,  and it's not at all "aspirational" to create acidic water- it's easy. Others of us have "liquid minerals" water spewing from our faucets, and an RO/DI unit is pretty much the only way we're ever going to venture towards that destination.

A Lot of people ask about utilizing leaves and other botanicals to lower the pH in their aquariums  As you are no doubt aware by now, many of these natural materials release substances such as  tannic and humic acids into the water, which can acidify it- IF the water has a low enough KH. Most botanicals won't do much to significantly reduce the pH if you start with hard, alkaline water, as the KH will prevent the acids released by these materials from reducing the pH. In general, it's fairly safe (gulp) to state that soft water is usually acidic, and "hard" water is usually alkaline.

Soft, acid water...It even sounds kind of cool, doesn't it?

Low pH water...the "jumping off point" for the hardcore fish keeper, right? A land where all sorts of possibilities exist...Where Altum Angels and Wild Bettas play. A land where replicating a peat swamp in Borneo or an igarape in Brazil are totally achievable. A realm where, yeah, leaves and botanicals can have a serious impact.

Low pH. 

This is currently the realm of super-experienced, highly experimental hobbyists, who are perhaps trying to unlock secrets of very demanding fishes, such as Altum Angels and others, which are known to come from and thrive in pH levels below 5.0. And, to achieve and maintain such pH levels, we're learning that the careful administration of acids, and the application of other exotic and scary-sounding techniques is required.

And the management of low pH systems, with the additional benefit of humic substances provided by botanicals, is a real "frontier" in the hobby. Even in the greater context of the blackwater aquarium world, it's seen as such. It can be challenging. But it's not the frightening sideshow it once was.

I mean, it sounds a bit scary, right? What exactly is the challenge here, besides getting the water to your desired target pH?

Understanding water quality management and the way in which denitrification occurs in closed systems in very low pH is challenging. On the surface, it seems really scary and daunting. I can't help but believe that- like so many things in the aquarium hobby-it's more of a function of the fact that we haven't done much with this in the past, and we simply don't have a "path" to follow just yet. We need to understand a different class of organisms which "run the cycle" in this environment, and how to manage them.

I suspect, that at some future point, there may indeed be more specific procedures, and perhaps even products available to manage the water quality, nitrogen cycle, and overall aquarium environment in lower pH systems. It's a highly specialized area, but one which seem to be getting more and more attention from the hobby. And really, we've seen hobbyists venture into "difficult and scary" hobby specialties before...Will the low pH blackwater/botanical-style system be the "reef aquarium" of the 2020's? We hope!

The other day, a hobbyist contacted me about the process of nitrogen cycle management in the lower pH aquarium; how it works and how we could get a cycle going...And of course, it made me once again want to kick myself in the ass for sleepwalking through biology class in college...but it also got me thinking. Specifically, he was concerned that the "bacteria in a bottle" products that are available commercially for the purpose of kick-starting the nitrogen cycle in our tanks typically don't function at lower pH levels.

It got me thinking about the nitrogen cycle and how it works in our blackwater, botanical-style tanks, and the importance of going slowly, observing and testing, and understanding where the potential pitfalls are which can (on rare occasions, fortunately) cause bad outcomes in aquariums.

I mean, we all should have at least a rudimentary working knowledge about the nitrogen cycle and how it works in our aquariums. There are numerous articles written about that in hobby literature by people who have forgotten more about it than I'll ever know, so I'll assume you have that down..

I've personally never managed a system with a pH much below 5.5 pH; this is where the "outer limits" of low pH aquariums starts for most, and this is likely the realm of Archaea, as the Nitrosomanas and Nitrobacter barely function at that point. We've seen advanced aquarists depend upon chemical filtration media to manage organics at these extremes.

And once again, I think that the real key ingredient (besides knowledge) to managing a low pH system (like any system) is our old friend, patience! It takes longer to hit an equilibrium and/or safe, reliable operating zone. Populations of the organisms we depend upon to cycle waste will take more time to multiply and reach levels sufficient to handle the bioload in a low-pH, closed system containing lots of fishes and botanicals and such.

This certainly gives the bacterial populations more time to adjust to the increase in bioload, and for the dissolved oxygen levels to stabilize in response to the addition of the materials added-especially in an existing aquarium. Going slowly when adding are botanicals to ANY aquarium is always the right move, IMHO. Period. Full stop.

And at those extremely low pH levels?

You might need to depend upon...Archaens.

Who? Huh?

They sound kind of exotic and even creepy, huh?

Well, they could be our friends. We might not even be aware of their presence in our systems...If they are there at all.

Are they making an appearance in our low pH tanks? I'm not 100% certain...but I think they might be. Okay, I hope that they might be. 

So, what are Archaens?


Archaeans include inhabitants of some of the most extreme environments on the planet. Some live near vents in the deep ocean at temperatures well over 100 degrees Centigrade! True "extremophiles!" Others reside in hot springs, or in extremely alkaline or acid waters. They have even been found thriving inside the digestive tracts of cows, termites, and marine life where they produce methane (no comment here)  They live in the anoxic muds of marshes (ohhh!!), and even thrive in petroleum deposits deep underground.

(Image used under CC 4.0)

Yeah, these are pretty freakin' crazy-adaptable organisms. The old sayings that "If these were six feet tall, they'd be ruling the world..." sort of comes to mind, huh?

Yeah, they're beasts....literally.

They're the crew who manage the nitrogen cycle in low pH environments.

Could it be that some of the challenges in "cycling" what we define as "lower ph aquariums" are a by-product of a sort of "no man's land" where the pH is too low to support a large enough population of functioning Nitrosomanas and Nitrobacter, but not low enough for significant populations of Archaea to make their appearance?


I'm totally speculating here. I could be so off-base that it's not even funny, and some first year biology major (who also happens to be a fish geek) could be reading this and just laughing...

Yet, I  still can't help but wonder- is this a possible explanation for some of the difficulties hobbyists have encountered in the lower pH arena over the years? Part of the reason why the mystique of low pH systems being difficult to manage has been so strong?

And then- you think about the pH levels in some natural, well-populated (by fishes!) blackwater habitats falling into the 2.8-3.5 range, you have to wonder what it is that makes life so adaptable to this environment. You have to wonder if this same process can- and indeed does -take place in our aquariums. And you have to wonder if we simply aren't working with these tanks in a correct manner.

Particularly, when they fall into what we'd call "extreme" pH ranges. I wonder if the "crashes" and fears and all sorts of bad stuff we've talked about in the hobby for decades were simply the result of not quite understanding the "operating system?"

I'm kind of thinking so.

Things just work differently at those lower pH levels- in nature, and in our aquariums.

Suffice it to say,  it's not "disaster time" when you get into this range- it just requires greater understanding and a different approach to nitrogen cycle management. Taking the time to learn about the arena in which you're playing. Learning the rules and dynamics, and adjusting your practices to accommodate the requirements dictated by these parameters.

Or, as one of my buddies so eloquently put it during one of those alchohol-fueled fish conference discussions some years back, "The idea is not to kill fish with this shit..." Yup. You don't "dabble" in very low (aquaristically-speaking) pH systems-or any specialized aquatic system, really- without a game plan. Oh, and a pretty good understanding of chemistry- like, way better than what I have. 

Take the experience you've gained in other areas to this new frontier. Use that knowledge to push out further...

Read. Educate. It's out there on the internet. If you want it. You can find it, but it's not always easy to find. Google is a starting point. There are other places to search online, too. Please don't take "the easy way out" and simply email me for some kind of magical answer. I likely don't have one. Really. There isn't one. Knowledge often has to be gained by effort. Your own effort.

And often, experience.

Now, this is the part where you get more annoyed with me, because I offer little more than a challenge. A challenge to study, experiment, and learn. 

So this leaves most of us in a position of doing what we're already doing: Managing our soft, acid (in the "sixes") water aquariums in a manner consistent with good husbandry, going slowly when adding botanicals, and generally testing and observing our fishes. Ours is a world of balancing too much- and not as much as we want- a world of observation, measurement, continuous self-education and experimentation.

We can't be "casual" or "seat-of-the-pants" when we get to the lower pH ranges in the hobby. It's not "set and forget"...Active management is required. We don't enter this arena lightly, or "dabble" in it. I think we are all already aware that each and every blackwater, botanical-style tank requires thoughtful husbandry and a generalized understanding of water chemistry. And taking this body of knowledge and experience to the lower pH arena is a smart move.

So, when you've kind of got it figured out- and it IS entirely possible to do so- people may ask you that old question from the sixties, "Are you experienced?"

And you'll be able to tell them, "Yes. Yes I am."

Wouldn't THAT be a "trip?"

I think that it would. And a useful one, at that.

Stay brave. Stay undaunted. Stay educated. Stay relentless...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

January 29, 2019

Good question. I think that when you’re trying to reach those lower (by aquarium standard) pH levels, the two approaches would be 1) use MORE of whatever botanical you’re using, relative to the water quantity- preferably in a storage container, as opposed to your display, or 2) do some research on those who are playing with acid solutions (Ted Judy comes to mind) and, IF you’re up to it, of course (it’s some SERIOUS stuff!).

Good luck!


Mark Cousins
Mark Cousins

January 28, 2019

Compliments!Very interesting article!😉
I have a tank which I set up at the beginning of December.I used RO water,PH was 6.5.I have been trying to slightly lower the PH,using Cattapa leaves and bark and also alder cones.Have managed to get about PH 6.But was hoping to reach 5.5 for liquorice gourami.Any tips on how to aid lowering the PH.
The tank still does not contain fish.

Mark Cousins

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