What causes that "haze" in botanical-method aquariums?

We talk an awful lot about the color of the water in our botanical-method aquariums, don't we? It makes sense, because the color is truly one of the big "aesthetic attractions" of these types of systems. 

However, there is another issue which is quite common in botanical-method aquariums- a sort of "haziness" to the water. Particularly in the earliest phases,  botanical-laden aquariums seem to have a "haze" that is slow to clear.

What causes this?

Now, part of this haze is no doubt due to the breakdown of the leaves, pods, etc. that we use. Surface dirt, lignin, sugars, and other compounds, bound up in the tissues and multi-faceted structure of the botanicals, is released into the water upon the initial submergence of these materials. And, the fact that many of us tend to not use a lot of chemical filtration media in our tanks might have some impact on that, as well.

As these materials begin to decompose, they release many of their constituent chemical components into the water, which of course, has a visual component that we all see. 

So, is this a problem for our "aquariums?"

Well, it usually isn't a problem in my experience, but I suppose that it could could be. I mean, if you have a significant quantity of organic materials- bioload- accumulating in your tank, water quality could be degraded. Concerned about what the "haze" or cloudiness means for the water quality of your tank? Conduct some water quality tests. 

Another reason for this haziness could be a burst of microorganism/bacterial growth, which impacts the visual clarity as populations multiply rapidly in the "fertile" environment of a botanical system, with its wealth of organic materials supplied by the decomposing matter upon which these life forms feed.

Now, I have placed a few drops of tank water under a microscope early in the life of several botanical-style tanks, and I did see quite a bit of microorganisms swimming around in there. Of course, I am not a microbiologist, and for me to make any conclusive statements about "density" or "diversity" of the life forms I saw swimming around in my samples is a bit too amateurish! That being said, in most of these samples, I saw a lot of "some sort" of life forms swimming around in the water! 

Generally, I've found that the sort of "cloudiness" will typically clear after a week or two, as the "tug of war" between bacteria and "infusoria" achieves a sort of "equilibrium."

At this point, I should mention that you could intervene in this if you wanted to...Performing larger water exchanges, employing chemical/very fine mechanical filtration media, etc. Personally, I have learned over the years NOT to let this stuff phase me. I suppose I'm so deep in my own "mindset" about letting nature do its thing, that I don't do much to combat it...

Once this initial "microbial haze phase" passes, there are other aspects to the water clarity which will continue to emerge. And I think that these aspects are similar to what we observe in nature.

For example, I've noticed that in many of my aquariums, particularly those with certain types of wood (like mangrove, newer Mopani, etc.), you'll get more of this "patina" to the water. Again, I'm in the realm of speculation here, but I can't help but wonder if certain wood and botanical materials/leaves have a greater content of organic materials (or more readily release these materials into the water because of their structure), lignin, tannins, etc.

One of my friends calls this "flavor", and his moniker makes sense, when you think about it!

And I think that this is a really interesting phenomenon, which is distinctive to our botanical-stye blackwater/brackish aquariums. To accept it is a choice, and it definitely requires the adoption of a mindset shift to appreciate that this is very similar to what we see in many of the natural aquatic systems that we attempt to replicate.

Of course,  an aquarium is NOT an open, natural system, and that there are fundamental differences between the two. However, to see some of the processes, aesthetics, and what we call "functional analogies" (i.e.; the way materials break down, re-distribute within the tank, and how the aesthetics and water chemistry are affected by water exchanges, etc.) take place in our aquariums, we can't help but think that we're "on to something" here.


Actually, we've talked about it a lot here, but I think it's something that's going to always come up in our little hobby speciality. 

At this point, even though it sounds a bit redundant- let's sort of summarize what contributes to this stuff...

The reality is that, IMHO, many of the causes are biological in nature. In the case of our botanical-method aquariums, the cloudiness could also be caused, at least in part- by the dissolving of the botanicals themselves. Most plant parts, such as seed pods and such, are comprised of materials such as lignin, cellulose, etc., and their constituent sugars, starches, etc. And, because of this composition, will release these materials into the water column as they break down.

Now, this haziness, in general, may be a "tip off" to some other issues in the aquarium. And, as we all know, it 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 hazy or cloudy water in virtually every situation is similar: Water exchanges, 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.

Of course, with the haziness or "cloudiness" caused by our "technique" or application of botanicals is a slightly different story. These are sort of "natural consequences" of what we do..

In Nature, we see these types of water characteristics in a variety of habitats. While they may not conform to everyone's idea of "beauty", there really IS an elegance, a compelling vibe, and a function to this. 

Fish don't care that their water is tinted, a bit turbid, and sometimes downright cloudy, as long as the other environmental characteristics of the water are satisfactory.

As we've discussed a lot lately, we're absolutely obsessed with the natural processes and aesthetics of decomposing materials and sediments in our aquariums. And of course, this comes with the requirement of us to accept some "unique" aesthetic characteristics, of course!

It's almost like our idealized aesthetic perceptions of what we feel water should look like in an aquarium have conditioned us as a hobby to sort of gently disregard what it truly looks like in the habitats from which our fishes evolved.

So, regardless of what causes the "haze" in your aquarium, keep a clear focus on what's really important- the health of your fishes, above everything.

Stay dedicated. Stay thoughtful. Stay observant. Stay patient...

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


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