We really need to talk...

It seems that everywhere we turn, there is a growing interest in adding "twigs and nuts" to our aquariums, with more and more aquarists considering (and actually creating!) a botanical-style, blackwater aquarium. This idea, formerly a sort of "side show" novelty, is rapidly moving into the mainstream of aquarium technique, and lots of interesting developments are happening.


This is really cool!

Of course, whenever you see something becoming an emerging "trend" (Gulp! I HATE that word when used in the context of an aquarium topic!), you will see hobbyists making incorrect assumptions, having general misconceptions, and occasionally, unintentionally spreading wrong information about stuff. It's often a function of the fact that some of this stuff has been either misunderstood or under-appreciated for some long that we've simply not really considered the dynamics involved in this context. 

Totally understandable, really.

And of course, being one of the leading proponents (and arguably, one of the more visible ones!) of this type of aquarium keeping, we have an obligation to the hobby community to provide correct information and clarification whenever possible, and to advise when we think something that's bandied about might be incorrect. One of the best ways to "keep it real" and address this kind of stuff is simply to tell it like it is!


Here are a few topics that we've seen discussed recently which, in our opinion, need to be clarified and thought through a bit before making conclusions. Obviously there are many more topics, and we could probably write a column on each one of these!

Yet, here's a start; the beginning of a dialogue which might provide some clarity on some important aspects of the blackwater, botanical-style aquarium:



1) Botanicals cannot soften hard water. This is one of the more persistent misconceptions floating around. It started decades ago, with hobbyists thinking that leaves could do it, and it's continued right up until the present. Now, it's thought that materials such as peat moss act to some extent as  a sort of "ion exchange resin, removing some minerals from the water and replacing them with humic acids, and perhaps this is where the idea that "all botanicals" can influence water chemistry accordingly arises. Botanical items (leaves, wood, seed pods, cones, etc.) do contain tannins and humic substances, and if used in sufficient quantities, can certainly lower the pH somewhat in water which is low in carbonate hardness.

However, these botanicals themselves simply cannot measurably lower the hardness of your water. That needs to be accomplished by a process ion exchange (such as reverse osmosis/deionization). If you start with hard, alkaline source water (which contains lots of dissolved minerals), the botanicals will essentially do nothing to remove them. Soft water is water that contains low levels of dissolved minerals, and as such, has lower ability to absorb acid substances, which will accumulate and lower the pH. That's why the effectiveness of botanicals in lowering pH can be significant in soft water. 


2) Don't let the tint fool you. Remember, the visual color change imparted to the water via the aforementioned tannins is not an indication that you have soft, acidic water. In the absence of chemical filtration media such as activated carbon, which remove coloring agents from the water, the tint will be most evident as these materials enter the water. However, don't forget that you can still have very hard, alkaline water and have some color. Just look at your municipality's annual water report...they actually mention visual tint" in their assays. So I guess one could call tint a "vanity metric" (to steal a marketing term) in that it's really an observation of cosmetic appearance versus a manifestation of functionality.


3) There is no "recipe" for how many botanical materials will accomplish a given affect within your aquarium water. Yep, we've mentioned this dozens of times, and it warrants repeating. Although we can make crude estimates based on personal experiences with regard to how many leaves (for example) it took to lower our pH from ___ to ___ in water with little to no general hardness, it's both unrealistic and misleading for anyone to suggest specific numbers of various botanicals can give you a specific effect.

If for no other reason than the fact there are countless variables in everyone's aquarium and water, and that the botanicals themselves, being natural materials, may have varying levels of pH-affecting tannins and such in a given sized leaf (as one example), we just can't quantify this. You need to start off with what seems to be a reasonable number of materials and test your water regularly to determine the impact on your aquarium. All changes need to be done slowly and carefully.


4) The creation of food webs is interesting, but is not spontaneous or even a "given" when utilizing botanical materials in your tank. Sure, we spend a lot of time talking about the concept of creating a system which facilitates the growth of significant quantities of organisms (such as microorganisms, fungi, small crustaceans, worms, and aquatic insects), but the reality is that just throwing in leaves and seed pods isn't the whole story. Sure, as they decompose, they'll fuel some microbial growth, and generate biofilms and fungi. However, you'd likely need to "inoculate" your system with small crustaceans like Daphnia, Cyclops, Gammarus, etc. in order to have more complex and diverse food sources available to your fishes. And you'd need to do this prior to adding fishes (which will consume them rapidly!), or in the confines of a separate "refugium" installed solely for the purpose of cultivating these life forms.


5) Botanicals will not give your aquarium a permanent, stable hardscape! Nope, by their very nature, these materials begin to break down as soon as they hit the water, so the "clock is ticking" as they say! Now, some materials (the more durable seed pods, etc.) will last longer than say, leaves, which break down in a matter of weeks. However, the vast majority of botanicals all begin to decompose and physically change appearance over time. And this is a cool thing, really...this is exactly what happens in nature. These materials create what could best be referred to as an "ephemeral" hardscape. One which might well be anchored by permanent pieces like rocks and driftwood, but is accented by the changing condition of the botanicals.

We like to refer to this as an "evolving" aquascape, and I think that's pretty accurate. And it reflects both the charm and attraction of the blackwater, botanical-style aquarium. Unlike many "traditional" aquascaping approaches, a significant part of the appearance of the tank is driven almost solely by nature, and as such, will change as materials break down, are moved about, and/or covered with biofilms and algae. This is exactly what happens in the wild, and is why we say that operating this type of aquarium requires a distinct "mental shift!" Now, you can of course, keep your aquascape looking pretty close to the way it started out if you regularly remove, clean, or replace the botanicals. However, this level of "intervention" may not appeal to everyone!



6) Botanical-style aquariums are not set and forget systems. Look, you're talking about a tank with (typically) soft, acidic water, a fish population, and a large quantity of materials which are breaking down. This number of variables requires regular observation and management on the part of you, the aquarist. Now, I personally have never had a "crash", or seen rapidly rising nitrate levels in an actively managed blackwater, botanical-style aquarium, but the reality is that  you're going to have to get your hands wet.



Over time, these tanks seem to reach a sort of "equilibrium", where you won't see significant parameter swings or changes. The bacterial population adjusts to the amount of materials in the tank, provided you don't continuously add stuff or make sudden, abrupt changes in procedure. However, like in any system, this is largely because of the work of the aquarist to keep things humming along. These tanks are no more inherently unstable or "dangerous" (something we've heard in the past about blackwater/botanical-style tanks) than any other system. You just need to understand the dynamic, accept the limitations of a given tank, and to not expect to simply "sit back, relax, and enjoy the flight" as they say. Stay consistent, involved, observant, and above all, patient, and you'll be just fine. 




Sure, I could probably go on and on and cover all sorts of different, rather arcane topics within this context, but I think we've addressed the most important and common ones. And hopefully, this provides a contextual framework for you to explore and discuss more about the design, construction, and management of botanical-style blackwater aquariums. 

It's an exciting, evolving are of the hobby, breaking out of the shadows of misconception and obscurity. This takes time. It takes patience. It takes understanding...and lots of sharing of information.

Yeah, we really need to talk!

Are you up for it?

Stay involved. Stay excited. Stay curious. Stay diligent.

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


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