Mangrove meanderings: A closer look at utilizing mangrove materials in the blackwater aquarium!

One of the things I've really enjoyed lately is discussing the work on my own aquariums, and the trials and tribulations which accompany them. Our blog yesterday about my latest home blackwater aquarium seemed to generate a lot of PM's and email about the use of some of the materials I selected, specifically Mangrove leaves and wood...

So, it seemed as though it would be a good time to go into just a bit more detail on them!

Now, with the mangrove leaves, it's sort of interesting...I admit that I selected them for this freshwater aquarium for two reasons: First, they look really coo, providing a sort of "generic" kind of "tropical look" for the tankl! And second, there are instances of mangroves in freshwater habitats, so it would be worth experimenting with them in this tank for "performance" purposes (i.e.; how they break down, impart some tint to the water, accrue biofilms, etc.). 

It was important to think of them in the context of a brackish mangrove habitat first, and to consider just how this applies to our blackwater world. 

As in our blackwater systems, fungi and bacteria in brackish and saltwater mangrove ecosystems help facilitate the decomposition of mangrove material. Interestingly, in scientific surveys, it's been determined that bacterial counts are generally higher on attached mangrove leaves than they are on freshly-fallen leaf litter, and this is kind of interesting, because ecologists feel that attached, undamaged mangroves leaves don't release much tannin, which, as we know might have some anit-bacterial properties. However, it's also been found that materials like humic acid, which are abundant in the mangroves, stimulate phytoplankton growth there. 


So, armed with this sort of information, I went ahead and figured I'd give 'em a shot. And the bottom line is, they work great! A lot of people wondered if there would be any release of salt from the leaves, and I knew that there likely wouldn't be, because a) root membranes in many species prevent salt from getting into the plant in the first place, and b) some species, such as "White Mangroves" (which we don't use), develop thickened succulent leaves, discarding salt as the leaves eventually drop.

Their tissues may have above average tolerance for salt, but most mangroves use one or more  "active strategies": Exclusion, excretion and partitioning. Exclusion means drawing in water without drawing in the salt ions. Their unique root structures allow them to perform this function efficiently. Excretion means being able to transport salt to organs "glands" where it is concentrated and actively expelled. Partitioning means that salt within the plant may be blocked more from some tissues than from others where it may be allowed to accumulate. In some species, senescent (aged) tissues, such as old leaves, accumulate salt before being dropped by the plant.


Most mangrove species will also grow in fresh water (and occur far up tidal rivers). Most species can also be killed by excessive salt ... as occurs due to evaporation in some shallow (intermittently tidal) habitats. Although they are adaptable plants, there are limits to this adaptability, apparently. So, in the end, you can sprout and grow mangroves in blackwater systems, for those of you who are so inclined, BTW! In fact, I'm doing it right now...


So the reality is that by the time we utilize the dried, fallen leaves, there is no salt in them. And, if there were, it would be released out in the preparation process anyways! This makes sense, as even with my trusty digital refractometer and the introduction of unprepared Red Mangrove leaves into a container of straight reverse osmosis/deionized water resulted in no detectible salt concentration, even after several days.

It makes sense, of course, because, as mentioned above, by the time the leaves fall from the Mangrove trees, and salt has already been released.

And from a durability standpoint, in my experience, they last a good long time submerged. Even though the Red Mangroves, in particular, are a bit more "crispy" when we receive them than the "Yellow Mangroves", they last for several weeks before softening. I've had them last well over a month before breaking down...Now, that's hardly scientific, and can vary from tank to tank based on many factors, ranging from water parameters to the infauna and fish population. However, for our general interpretation, this assessment is "accurate enough", lol.

As part of our "Estuary" line of brackish-water materials, we've been offering Red Mangrove root sections for some time. Just what they sound like- these are thick, woody sections of the prop root of the mangrove tree, and they are cut into little "log-like" sections, varying in both size and thickness. However, they are much, much thicker and more "substantial" in general.  We occasionally get some larger, more "curved" root pieces (premium ones), which are awesome, too.

The bulk of the bark will be stripped away from these root pieces. They are available in two sizes, "Regular", with lengths of 12 to 18 inches (30.48- 45.72cm) and an average diameter of 1.25 inches (3.17cm)  and "Large", with lengths of 16 to 24 inches (40.64- 60.96cm), and an average diameter of 1.75 inches (4.45cm). You'd use these in conjunction with the thinner branch sections to create a more "complete" look for your habitat...and that can include their use in a "straight-up" freshwater tank!

And, with mangrove root sections, the same physiological processes and factors apply. You're unlikely to find much residual salt in them. I never detected any leaching of salt at any level in my aquarium, despite extensive use of mangrove roots for the hardscape. 

One thing that I have observed in regards to utilizing the mangrove root sections in my aquariums is that they tend to accrue biofilms and even some "beard algae" much more significantly than some of the other wood we use for this purpose (ie; Manzanita, etc.). I personally feel that this is because mangroves grow in very nutrient-rich habitats, and have very efficient internal structures and tissues to transport and store nutrients. And I think they have "pockets" of locally-stored nutrients in their surface tissues which facilitate the growth of these life forms.

Consider that, when the roots are chopped away from actively-growing trees (As ours are. Remember, they're legally acquired from the City of Honolulu, removed as part of their attempts at eradication of the Red Mangroves- which are an invasive species in Hawaii), they may contain some of the stored nutrients and other materials in their tissues, which, at least in theory, could leach into the water column over time.

And, these roots do leach tannins into the water, much like any other wood- but in a very noticeable amount! You'll get some real nice reddish-brown "tint" from them! That's cool, but I understand that some of you may have concerns about the surface "biocover..." So, if I were you, I'd probably handle the wood differently than I did before using it in my aquarium (I literally added it to my tank, filled it, and called it a day). I'd probably let these roots saturate for a few weeks in a container of  fresh water, at least letting them re-saturate and perhaps release- or begin to release- the bound-up materials and organics contained in the their tissues.

In the end, both of these mangrove-sourced materials can certainly be utilized in your blackwater, botanical-style aquarium, with the typical due consideration paid to preparation, and the understanding of how they will react within the closed system aquarium. 

Like everything we do in this realm, use of mangrove materials is an "evolving" art, which puts you- the user- squarely in the "bleeding edge" of aquaristics when playing with this stuff! You are making literal "ground floor" contributions to the "state of the art" in our botanical-style aquarium "practice" when you incorporate some of these materials into your system!

So, if I haven't yet freaked you out with talk of algae, biofilms, and organics...I say, give mangrove materials a try in your next FRESHWATER system (well, "tinted" freshwater, that is!).

Stay experimental. Stay cutting edge. Stay creative. Stay excited...

And Stay Wet!


Scott Fellman

Tannin Aquatics 



Scott Fellman
Scott Fellman


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