Where's all the algae?

Like any other type of aquarium methodology, the botanical-style aquarium requires diligence and follow-up. You need to keep on top of some things.Now,  It's not like your aquarium is teetering on the brink of failure; you just need to monitor the water parameters and observe. 

Yet, for some reason (likely, the aesthetics) aquariums which embrace this methodology seem to be viewed by some as undisciplined, sloppy, and even managed haphazardly. The reality is that these are some of the most stable, easy-to-maintain aquariums you can set up. The key is patience and having a good understanding of how these systems work.


Like, how they embrace natural processes. You know, the kind that have been occurring in Nature for eons.

And the broad descriptor, "natural processes" includes the growth of every aquarist's least favorite aquatic organism, algae! 


Readers have told me that I haven't touched on what they consider to be one of the more interesting "benefits" of a blackwater aquarium that many of us have experienced:

The fact that the occurrence of nuisance algae outbreaks seem to be relatively rare in these systems. And they're correct, this is an interesting topic that I have briefly touched on, but never really went into a lot detail about.

And it's always  controversial, too!  

'Cause it's algae, man.

It scares the living shit out of almost every hobbyist.

There are countless forum threads, magazine and online articles, and lectures all about algae and algae control. The causes and techniques for control seem to be pretty well known in the hobby, and covered in intimate detail by experts far more learned than I. We're not going to touch on every nuance of a subject that's been well-covered in the hobby for over a century.

Rather, lets talk about algae relative to the types of aquariums we play with!

While it would be intellectually dishonest (and just plain untrue) for me to assert that blackwater/botanical aquariums aren't susceptible to algae outbreaks, it is sort of remarkable that we simply don't have massive algae issues in these types of aquariums on a regular basis, right? I mean, we have tanks in which we willingly dump in large quantities of botanical materials, which certainly increase the biological load of the aquarium.

You'd think that this would be pretty much a recipe for an algal bloom of epic proportions.

Now, I have to admit, that I have never had one of those nightmare algal blooms in a blackwater aquarium...and although it sounds like tannins or some other "substances" in the blackwater would be the obvious "x factor", I'll tell you that I've personally never had a major algae outbreak in any of the other types of aquariums I work with, either. Now, let's be clear:  I'm not saying that I've never had algae issues in any of my tanks. Of course I have.  I've just never had one of those "I'm ready to tear down my tank and quit the hobby" kinds of algae blooms.

(Like, I'd ever quit the hobby because of something stupid, like algae! C'mon.)

So, from  personal standpoint, I can shout, "My blackwater tanks don't have excessive algae issues!"

However, they do have some algae from time to time.

Of course.

So, what kinds of algae do I see in my botanical-style aquariums which have tinted water?

For one thing, I will get the algae on the glass in some of them. You know, that easy to wipe away, diatom-like stuff. Notice I said "diatom-like", because I'm not 100% certain that it is. Since I'm not a professional biologist, I can only wonder exactly what this stuff really is.

Diatoms tend to rely on phosphates and silicates for growth- two compounds which are lacking in my source water. How diatoms can appear in tanks in which I use reverse osmosis/deionized water, produced by an RO/DI unit which has a specialized resin cartridge to remove silicates and phosphates, for that matter- leaves me wondering.

Of course, phosphates come from foods, so I can see why I might encounter it on occasion in my tanks. Although my phosphate levels in most of my freshwater tanks are undetectable on high-end hobby test kits/checkers.

Anyways, it generally takes a couple of weeks to accumulate to the point where I feel it necessary to break out the algae scraper. I think that the fact that I don't use high intensity lighting on most of my botanical-style tanks not only limits some algae growth, but it makes it more difficult to see as well!

I have to admit that I've  never encountered those Bryopsis or so-called "Black Beard Algae"growths. For some reason, it's not something that tends to grow in my tanks. I could speculate why, but I'd be doing just that- speculating. Likely its some combination of nutrients and lighting- perhaps even water movement. Hard to say, right?

And then there is the well-known "hair algae" or "thread algae" as it's commonly known to hobbyists. The causes, as usual, of this algae are thought to be excessive light and nutrients, like iron, phosphate, etc. I know those of you who keep planted tanks despise the stuff.

Now, I can tell you that the only time I've encountered this in a botanical-style aquarium was in a tank which had plants, and in which, in the name of experimentation, I deliberately cranked up the lighting intensity to a level far in excess of what was necessary to grow the few plants present in the aquarium.

Yeah, the stuff made its appearance. And it left very quickly once I dialed down the lighting, FYI. 

Now, one thing that we might encounter now and again, particularly in newer aquariums with lots of botanicals and sedimented substrates, is a little "dusting" of sediment on the walls of the tank. It's usually just that- sediment and some bits of botanical materials which get mixed into the water column after set up and settle on the walls of the aquarium, and on the leaves and wood.

This should not be confused with algae.

And the same thing happened in Nature. Always remember that.

And of course, biofilms and fungal growths, ever-present in botanical-style aquariums, need no real introduction to most of our followers. We just need to understand how and why they form, and what they mean for the ecosystem of our aquarium. And we need to understand that not only are they desirable, they are to a certain extent "self-regulating", and you'll often only see them if you look really carefully for them.

Unlike fungi and biofilms, in general, most algae tend to rely on nutrients and light, and will grow more extensively when higher amounts of both are available. We know this basic premise from our earliest days in aquarium keeping.

Yet, why don't you commonly see large amounts of algae in blackwater aquariums?  For that matter, how come you don't see huge algal growths in blackwater systems in Nature? What factors contribute to or limit their growth in Nature?

You may or may not be surprised.

I read a study from the University of Georgia, which examined the apparent limited amount of algal growth in blackwater streams, to determine if the limiting factor was chemical (nutrient) or light-driven...and lo and behold, the study concluded that it wasn't necessarily some magic stuff in tannins and blackwater that inhibited algae growth, as much as it was light limitation! 

Yeah, the light-limiting effects of the blackwater itself were discovered to inhibit algal growth in coastal plain streams. As light penetrates the water, high dissolved organic compound concentrations and suspended solids can scatter and absorb light, impacting algal growth significantly. 

Okay, sounds like a bummer if you want to believe blackwater is "magic", but the study also concluded that blackwater systems were somewhat nutrient-limited, which also affected the growth of algae- although this was not concluded to be the primary factor which inhibited algae growth.

In fact, another study I perused about the Rio Negro concluded that it was found that there is a relatively small difference in "respiration rates" between "whitewater" and "blackwater" rivers, and that the presumption that blackwater systems are more "sterile" is sort of...overstated. 

There is a lot of potential organic "algae fuel" there, despite limited concentrations of certain ions and trace elements. Yet, nutrients- be they organic or inorganic- are only part of the equation for algal growth.

Interestingly, the study also concluded that higher incidence of algal growth occurred in areas in Amazonia where water movement was minimal, or even stagnant, suggesting that, all things being equal, light limitation and water movement are possibly more significant than just higher nutrient concentrations alone!

And that makes sense, if you consider the long-held belief within the aquarium hobby that most plants don't do well in blackwater aquariums "because they don't get enough light!"


So the long-held aquarium attitude about blackwater having some algal-inhibiting properties is really based on the fact that it's...darker? I mean, every blackwater/botanical-style aquarium I have ever owned does have some algae present. Although, being a reef guy at heart, every aquarium I own has good water movement. In leaf-litter-dominated aquariums, which I love, I still keep a good amount of flow going.

This is interesting, because you'd think that an aquarium dominated by decomposing leaf litter would be a veritable "algae farm", right? And yet, I've experienced no more occurrence of algae in the leaf litter tanks than I have in other setups. On the other hand, regardless of what type of system I work with, I'm fanatical about husbandry and nutrient control/export...obviously, another key factor.

As you know by now, the ecology of the botanical-style aquarium is all about facilitating natural consumption of nutrients via biofilms, fungal growths, and other  organisms. In other words, algae has to compete for available nutrients with a whole host of organisms! And algae doesn't always win. Even in circumstances where you might think it could.

Interesting stuff, huh?

The very composition of our botanical-style aquariums is likely the biggest reason why these tanks tend not to grow large amounts of "nuisance algae."

Of course, there is still the light factor, right?

Since a lot of blackwater/botanical-style tanks are hardscape only, with little or no aquatic plants present, the lighting we are employing is often strictly aesthetic, right? So, you're not hitting a tank with decomposing pods and no plants with 14 hours of high intensity full-spectrum light...


Well, that certainly can be part of the reason why our botanical-style aquariums magically have essentially little to no nuisance algae, huh? We pin both the praise and the blame for algae on the wrong suspects, I think! 

Man, this deserves more study...a lot of it.

And with more and more hobbyists playing with planted blackwater tanks, we'll have a greater "body of work" from which to draw. For that matter, more botanical, blackwater tanks in general means more material to analyze! 

An there is another thing: As we've beaten into your head relentlessly, in our truly "natural style" tanks, we don't really care if there is some algae in there. We've made that "mental shift" that says it's okay to have some decomposing botanicals, brown water, biofilms, and yeah...algae. Because natural habitats do, too.

So it's not so bad, right?

The fact that we label it a "nuisance" IS sort of ridiculous, huh?

Let's think about algae in the aquarium to begin with...No, not the boring old "This is how algae problems happen in our aquariums..." lecture that you've read on every website known to man since the internet sprung to life. You can find that stuff everywhere. I don't need to deep-dive into how algae appears/grows, and how to get rid of it.

Rather, let's think about how we, as a group, mentally are opposed to the stuff in our tanks. I mean, yeah, I know of no one that really enjoys a tank smothered in algae. It looks like shit, and is a "trophy" for incompetence, in the eyes of most aquarists. In fact, I remember reading once that more people quit the aquarium hobby over algae problems than almost anything else!


Well, sure- algae problems caused by obvious lapses in care or attention to normal maintenance, like overfeeding, lack of water changes, gross overstocking, etc. are signs of...incompetence. The occasional algae outbreaks that many hobbyists suffer through have all sorts of other potential causes, and can often be traced to a combination of small things that went unchecked, and are typically controlled in a relatively short amount of time once the causative factors are identified.

Yet, as a group, us hobbyists freak out about algae in our tanks. I can show you a hundred pics of algae in the Amazon region for example, and say, "See it happens here too! Natural!" and the typical hobbyist will still be rendered speechless with horror.

And I can't even tell you what it would do to one of those "natural aquascaping" contest freaks or judges if you entered an aquarium with some algae growing in it! They'd lose their shit over that! People might die. You could be charged as an accessory to murder! 

So, not everyone gets it. Just like brown water, fungal growths, biofilms, and decomposing leaves. It's hardly a cause for celebration with many hobbyists. Yet, it's appearance does not signal doom. Algae, like all organisms, appears and flourishes when the right conditions are available. Simple as that. If you don't like the look of algae, you can attempt to limit its growth by addressing the potential root cause(s) of it's appearance.

Sure, "algae is the foundation of life", blah, blah, blah, and all that shit. Yet, it's also the foundation for a "cottage industry" of devices, chemicals, and treatment regimens designed to eradicate it quickly and decisively. When it appears in our tanks, we almost reflexively embark on strategies to eliminate it at all costs. 

I suggest that, despite our desire to eliminate it rapidly and entirely, we at least consider some of the benefits it can bring to the overall ecosystem that is our botanical-style aquarium. Stuff like supplemental nutrient export, food for fishes, and an indicator of the suitability of our aquarium for aquatic life.

Much like biofilms, decomposition, and fungal growth, we can make some mental shifts to understand, tolerate, and even appreciate what algae brings to the table. It's not always bad to have algae present. In fact, it would be bad NOT to have it present! We just happen to work in a hobby specialty that doesn't see a ton of it.

Tinted water is not a panacea, but it is a potential factor which limits excessive amounts of algae growth- both in Nature and in the aquarium. 

So, the key takeaways here are that:

1) Although there are many beneficial substances in blackwater, such as humic substances, tannins, etc., it's inconclusive if they alone are the reason (or even part of the reason) why we seem to have less incidence of algae in our blackwater aquariums. Some research suggests otherwise.

2) The light penetration limitation imposed by blackwater definitely has been shown to decrease or limit algal growth in the wild, and in the aquarium.

3) You still might see some algae in your tinted, botanical-style aquariums.

4) It's not a bad thing to have algae in your aquarium.

We can use a combination of understanding, acceptance, and good husbandry to manage its appearance in our tanks.

Let's consider algae control one more time:

Algae is super opportunitstic. That's why it's been around for billions of years. It waits for the proper conditions, and takes off when it's needs are met. In the closed system of an aquarium, algae blooms are simply caused by excess nutrients accumulating or being made available somewhere in the system, in conjunction with available light.

Simple as that.

And the solution is not fancy additives, manual removal, etc. It's isolating the cause of the nutrient excess and discontinuing or eliminating whatever practices, additions, or factors are contributing to it. So the "enemy"- the problem- is really not the algae itself (it's not attractive to everyone- I give you that.)- It's the circumstances that lead to its excessive proliferation in our systems.

That's the enemy!

Even in our sexiest, most well-maintained botanical-style aquariums, it's possible to have all of the ingredients for a good algae bloom! Because we use natural materials and allow other life forms to break them down. However, when there are excesses of what algae needs to thrive...it does just that.


Think about it- algae are merely exploiting what is there to exploit.

Take that away, and the excess of algae go "buh-bye!" Your mission:  Out hustle. Outcompete. Outwit. Outlast...Understand. Sounds like a the format of a successful reality TV show, but it's the key to control of excessive algal growth. Simple as that. Beat it at its own game with a life form that is more efficient at doing what the algae is doing. Take away the excess of whatever factor- nutrients, light, stagnation, etc., and the algae subsides.

Just think a bit differently about the problem. Easy.

Think about that simple idea before you reach for the bottle of algaecide or other exotic, complicated control technique.

Yeah, we have a lot of work to do to understand what algae is, how it becomes a problem in some tanks, and what it's not really much of an issue with botanical-style aquariums.

However, that's the fun stuff, right? A chance to learn, observe, and execute.

Stay diligent. Stay observant. Stay creative. Stay consistent...

And Stay Wet.


Scott Fellman

Tannin Aquatics 



Scott Fellman
Scott Fellman


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