Clearing up some stuff...

As enthusiasts of natural-style botanical-influenced aquariums, we are super-attuned to the color of our water. Most of us are into the dark-brown, tannin-stained water that characterizes so many wild habitats in the aquatic ecosystems of the world.

As you likely know by now, there are a number of factors which contribute to the color of the water in your blackwater aquariums; specifically tannins released by the leaves, wood, and other botanicals you have in your tank. As we have discussed now like, 327 times (okay, maybe less...)- in many situations, leaves and other botanicals will have little to no influence on pH (unless your utilizing a water source, such as reverse osmosis, which yields  product water with extremely low mineral content and is more "amicable" to pH reduction...).

However, they will affect the color and in some instances the visual clarity of the water. 

And color generally has absolutely nothing to do with the pH of the water, really.

Oh, and clarity...I know we've talked about the difference between clarity and color before, but let's hit on it one more time. I really want to see less of those, "I added a bunch of catappa leaves and seed pods from that vendor on eBay, and my water is a dark brown color, but the pH is still 7.6! What gives?" sort of questions that populate online forums worldwide.

It's a question that needs analysis from several factors, starting with the impact that botanical materials have on water chemistry (which we've addressed a bunch of times here), and encompassing their impact on quality, color and clarity.

And, much to the confusion of the aquarium world, they're all sort of interrelated.

We do have a sort of "historical bias" of just what aquarium water should look like. As aquarists, we were pretty much indoctrinated from the start that our tanks should have "crystal clear, blue-white water", and that this is one of the benchmarks of a healthy aquarium.

And of course, I won't disagree that "clear" water is nice. I like it, too...However, I would make the case that "crystal clear" water is: a) not always solely indicative of "healthy" or "optimum" , and b) not always what fishes encounter in nature.

The point is, we as fish geeks seem to associate color in water with overall "cleanliness", or clarity. The reality is, in many cases, that the color and clarity of the water can be indicative of some sort of issue, but color seems to draw an immediate "There is something wrong!" from the uninitiated!

And it's kind of funny- if you talk to ecologists familiar with blackwater habitats, particularly those in the Amazonian region which many of us love so much- they are often considered some of the most "impoverished" waters around, at least from a mineral and nutrient standpoint.

In the aquarium, the general hobby at large doesn't think about "impoverished." We just see colored water and think..."that shit's dirty!" 

And of course, this is where we need to attempt to separate the two factors:

Cloudiness and "color" are generally separate issues for most hobbyists, but they both seem to cause concern. Cloudiness, in particular, may be a "tip off" to some other issues in the aquarium. And, as we all know, cloudiness can usually be caused by a few factors:

1) Improperly cleaned substrate or decorative materials, such as driftwood, etc. (creating a "haze" of micro-sized dust particles, which float in the water column).

2) Bacterial blooms (typically caused by a heavy bioload in a system not capable of handling it. Ie; a new tank with a filter that is not fully established and a full compliment of livestock).

3) Algae blooms which can both cloud AND color the water (usually caused by excessive nutrients and too much light for a given system).

4) Poor husbandry, which results in heavy decomposition, and more bacterial blooms and biological waste affecting water clarity. This is, of course, a rather urgent matter to be attended to, as there are possible serious consequences to the life in your system.

And, curiously enough, the "remedy" for cloudy water in virtually every situation is similar: Water changes, use of chemical filtration media (activated carbon, etc.), reduced light (in the case of algal blooms), improved husbandry techniques (i.e.; better feeding practices and more frequent maintenance), and, perhaps most important- the passage of time.

So, yeah, clarity of the water is directly related to the physical dissolution of "stuff" in the water, and is influenced-and mitigated by- a wide-range of factors. And, don't forget that the botanical materials will impact the clarity of the water as they begin to decompose and impart the lignin, tannins, and other compounds from their physical structure into the water in our aquariums.

And in many cases, the water will not be "crystal clear" in botanical-influenced aquariums. It will have some "turbidity"-or as one of my friends likes to call it, "flavor."


Remember, just because the water in a botanical-influenced aquarium system is brownish, and even slightly hazy, it doesn't mean that it's of low quality, or "dirty", as we're inclined to say. It simply means that tannins, humic acids, and other substances are leaching into the water, creating a characteristic color that some of us geeks find rather attractive. If you're still concerned, monitor the water quality...perform a nitrate or phosphate test; look at the health of your animals. These factors will tell the true story.

You need to ask yourself, "What's happening in there?"

I believe that a lot of what we perceive to be "normal" in aquarium keeping is based upon artificial "standards" that we've imposed on ourselves over a century of modern aquarium keeping. Everyone expects water to be as clear and colorless as air, so any deviation from this "norm" is cause for concern among many hobbyists.

I can think of at least one or two other things that are influenced by the same processes, which we accept without question in our everyday lives...

People ask me a lot if botanicals can create "cloudy water" in their aquariums, and I have to give the responsible answer- yes.

Of course they can!

If you place a large quantity of just about anything that can decompose in water, the potential for cloudy water caused by a bloom of bacteria, or even simple "dirt" exists. The reality is, if you don't add 3 pounds of botanicals to your 20 gallon tank, you're not likely to see such a bloom. It's about logic, common sense, and going slowly.

A bit of cloudiness from time to time is actually normal in the botanical-style aquarium.

And, of course, what we label as "normal" in our botanical-style aquarium world has always been a bit different from the hobby at large.

In my home aquariums, and in many of the really great natural-looking blackwater aquariums I see from other hobbyists, the water is dark, almost turbid or "soupy" as one of my fellow blackwater/botanical-style aquarium geeks refers to it. You might see the faintest hint of "stuff" in the water...perhaps a bit of fines from leaves breaking down, some dislodged biofilms, pieces of leaves, etc. Just like in nature. Chemically, it has undetectable nitrate and phosphate..."clean" by aquarium standards.

Sure, by municipal drinking water standards, color and clarity are important, and can indicate a number of potential issues...But we're not talking about drinking water here, are we?

"Turbidity." Sounds like something we want to avoid, right? Sounds dangerous...

On the other hand, "turbidity", as it's typically defined, leaves open the possibility that it's not a negative thing:

 "...the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air..."  

What am I getting at?


Well, think about a body of water like the Rio Negro, as pictured above in the photo by Mike Tuccinardi. This water is of course, "tinted" because of the dissolved tannins and humic substances that are present due to decaying botanical materials.  

That's different from "cloudy" or "turbid", however. 

It's a distinction that neophytes to our world should make note of. The "rap" on blackwater aquariums for some time was that they look "dirty"- and this was largely based on our bias towards what we are familiar with. And, of course, in the wild, there might be some turbidity because of the runoff of soils from the surrounding forests, incompletely decomposed leaves, current, rain, etc. etc.

in the wild, there might be some turbidity because of the runoff of soils from the surrounding forests, incompletely decomposed leaves, current, rain, etc. etc.

None of the possible causes of turbidity mentioned above in these natural watercourses represent a threat to the "quality", per se. Rather, they are the visual sign of an influx of dissolved materials that contribute to the "richness" of the environment. It's what's "normal" for this habitat. It's the arena in which we play in our blackwater, botanical-style aquariums, as well.

Mental shift required.

Obviously, in the closed environment that is an aquarium, "stuff" dissolving into the water may have significant impact on the overall quality. Even though it may be "normal" in a blackwater environment to have all of those dissolved leaves and botanicals, this could be problematic in the closed confines of the aquarium if nitrate, phosphate, and other DOC's contribute to a higher bioload, bacteria count, etc.

Again, though,  I think we need to contemplate the difference between water "quality" as expressed by the measure of compounds like nitrate and phosphate, and  visual clarity.

So...we have to separate out the way our water tests from the way it looks.

My hypothesis:

Our aesthetic "upbringing" in the hobby seems to push us towards "crystal clear" water, regardless of whether or not it's "tinted" or not. And we associate clarity with quality.

A definite "clear water bias!"

And that's okay.

However, I think it's important to consider these factors in context. Particularly, in the context of the natural systems that we want to replicate in the aquarium. 

And, yeah- it makes sense to consider the roles of botanicals in this process, too.

As we've discussed before, the soils, plants, and surrounding geography of an aquatic habitat play an important and intricate role in the composition of the aquatic environment. They influence not only the chemical characteristics of the water (like pH, TDS, alkalinity), but the color (yeah- tannins!), turbidity, and other characteristics, like the water flow. Large concentrations become physical structures in the course of a stream or river that affect the course of the water.

And of course, they also have important impact on the diet of fishes...Remember allochthonous input form the land surrounding aquatic habitats? And the impact of humic substances?

I can't help but wonder what sorts of specific environmental variations we can create in our aquarium habitats; that is to say, "variations" of the chemical composition of the water in our aquarium habitats- by employing various different types and combinations of botanicals and aquatic soils.

I mean, on the surface, this is not a revolutionary idea...We've been doing stuff like this in the hobby for a while- more crudely in the fish-breeding realm (adding peat to water, for example...), or with aragonite substrates in Africa Rift Lake cichlid tanks, or with mineral additions to shrimp habitats, etc.

In the planted aquarium world, it's long been known that soil types/additives, ie;  clay-based aquatic soils, for example, will obviously impact the water chemistry of the aquarium far differently than say, iron-based soils. And thusly, their effect on the plants, fishes, and, as a perhaps unintended) side consequence, the overall aquatic environment will differ significantly as a result.

This is an area that I think we'll see much more work being done on in coming months/years. It really pushes us to think a bit differently and to apply unconventional solutions to our aquarium work.

Letting go of some long-held ideas and mindsets, and looking at Nature as an inspiration in both form AND function, as opposed to just looking at "the other guy's tank" for ideas, will pave the way for a new generation of natural-style biotope aquariums that will evolve and change the state of the art of our hobby for many years to come.

I think that, with a greater understanding of the types of environments our animals come from, that this "clinical sterility standard" for water and overall aesthetics of our systems will change. The movement towards biotopes and more naturally-appearing- and functioning- systems has opened the eyes of many aquarists to the amazing possibilities that exist when we move beyond our previously self-imposed limitations.

There's a lot of work to do here.

Stay resourceful. Stay open-minded. Stay curious. Stay creative...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


1 Response

Tamara Davidova
Tamara Davidova

June 26, 2019

Dear Scott! May be you will be interesting, one our girl is breeding crustacea, she use many leaves
In Russian, but google translate all texts)))
Sorry, my English is not very well

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