Color, clarity, and the stuff in between.

More mental shifts are required of hobbyists each and every day...

As more and more hobbyists embrace the use of aquatic botanicals in their aquaria, we're seeing more and more tanks with a golden brownish-colored "tint" to the water. I love that, as you all know.

However, let's be clear (arghhh!) about one thing:

There is a difference between "color" and "clarity."

The color is, as you know, a product of tannins leaching into the water from wood and botanicals, and typically is not "cloudy." It' actually one of the most natural-looking water conditions around, as water influenced by soils, woods, leaves, etc. is ubiquitous around the world. Other than having that undeniable color, there is little that differentiates this water from so-called "crystal clear" water to the naked eye.

Of course, the water may have a lower pH and general hardness, but these factors have no bearing on the visual clarity of the water.

I remember fondly, when I was co-owner of Unique Corals, a major coral importer/propagator, I had a beautiful little blackwater aquarium in my office. I loved that little tank. 

Everyone who came in my office gazed into that aquarium; most were hardcore "reef people" and marine livestock vendors. Their orientation was ultra clear, blue-white water...And if I had a dollar for every time someone told me, "Man, you MUST be busy! That aquarium looks pretty dirty. You need to change the filter...!"  I'd be filthy rich! Yeah. Once I explained what blackwater is and how it was natural and, in my eyes desirable, they would either have an "Ahah!" moment, or (more typically) just continue with the business at hand, shrugging off my explanation. 

Some hobbyists just don't get it!

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, 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..."dirty." 

And of course, this is where we need to separate 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.

There are of course, other factors that affect clarity, like fishes that dig or otherwise disturb the substrate and wood with their grazing activities, but these are not necessarily indicative of husbandry issues.

Okay, that was "Aquarium Keeping 101", actually.

Although we all seem to know this, I hear enough comments and questions about the color of the water and its relation to "cleanliness" in  natural, botanical-style blackwater systems that it warranted this seemingly "remedial" review!

Remember, just because the water in a botanical-influenced aquarium system is brownish, 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 test; look at the health of your animals. What's happening in there?

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 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 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.

Remember, too, that some "turbidity" in the water, in either a "whitewater" or "blackwater" system, is natural, expected, and not indicative of a problem. In many natural settings, water is chemically perfect but not entirely "crystal clear."  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.

In my home aquariums, and in many of the really great natural-looking blackwater aquariums I see 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.

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.

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 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.

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. 

A definite "clear water bias!"

And think about it: You can have absolutely horrifically toxic levels of ammonia, dissolved heavy metals, etc. in water that is "invisible", and have perfectly beautiful parameters in water that is heavily tinted and even a bit turbid. That's why the aquarium "mythology" which suggested that blackwater tanks were somehow "dirtier" than "blue water" tanks used to drive me crazy.

It doesn't bother me anymore.

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 systems has opened the eyes of many aquarists to the amazing possibilities that exist when we move beyond our previously-imposed limitations.

The future may not be "crystal clear", but I believe that it is bright and full of potential!

Much more to explore. Much more to learn. Much more to share here! 

It's about "reprogramming" ourselves just a bit- another "mental shift" that we have to make...

Stay open-minded. Stay curious. Stay observant. Stay bold...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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