"Any old leaf..."

As more and more of us expand into the botanical, blackwater aquarium world, it's only proper that more and more of us experiment with different things. Being both a "power user" and vendor of botanicals, I certainly consider myself fairly well-versed on a lot of this stuff (okay, as "well-versed" as one can be about adding "twigs and nuts" to his aquarium!). And, like you, I enjoy a good experiment or two, particularly when it comes to trying new botanical items for use in our aquariums!

I am often approached by hobbyists who found "such and such" a tree or bush in their yard, or while on vacation in Florida, or wherever, or from some other vendor, and ask me if the seed pods, roots, or leaves are suitable for use in aquariums. And honestly, most of the time, I give the same answer if I have not used the item in question:

"I don't know."

I get it. Hardly befitting on an answer from a guy who makes his living selling botanical items for use in aquariums, but it's the truth. There are around 400,000 described plant species in the world, and an average of 2,000 new species are described each year. I'm a fish geek, not a botanist, so understanding the physical/chemical/environmental impact of almost any plant is "beyond my pay grade", as they say! I can only speak in general terms. To assert otherwise would simply be irresponsible.

When we started Tannin, we had a good working knowledge of playing with some of these items in aquatic environments. Catappa (Indian Almond) leaves had been used for decades by fish people to impart tannins and humic substances into the water, as had guava and a few other leaves.

Now, it just so happens that Catappa has been studied pretty extensively by science, and it's generally acknowledged that there are some beneficial substances contained in the leaves and bark, many of which are known generally to have potentially medicinal properties. Now, keep in mind that these substances are present to protect the tree from fungi, bacteria, and parasites, so it's a bit of a leap when aquarists immediately extoll the virtues of them as fish remedies. Flavonoids, such as Quercetin and Kaempferol, which are abundant in Catappa, apparently have anti-inflammatory and possibly even anti-cancer affects, and anecdotally have been determined to be beneficial to fishes. I did come across a laboratory study from the Fisheries Ministry in Malaysia that determined catappa extract to be useful as a remedy and/or prophylactic for some fish diseases, so that vindicated some of the "anecdotal" stuff, in my mind.

You see tons of vaguely-worded articles on the purported "medicinal" properties of Catappa, typically on sites that, well- sell the leaves. And typically, they're muddy and filled with all of the wonderful marketing hyperbole and claims about their wonders that compounds the myths that are unfortunately so abundant in the aquarium world about this stuff.

We steer clear of this kind of vagueness, and rather, choose to focus on their use as aquascaping materials and as a means to impart tannins and humic substances from their tissues into the aquarium water, creating the visual tint and impacting some of its environmental parameters. Those are typically not disputable, with the exception of to what extent they do this.

And of course, we're ultra geeky about this, and that's why we offer what could only be described as "varietal" Catappa. I mean, where else can you find Terminalia kaerenbachii or T. litoralis? Yeah we geek out hard. 

And its the same with many botanical items you find in nature. Let's face it, most trees and plants have leaves, bark and seed pods which contain tannins and humic substances. To what extent, may only be determined by careful laboratory analysis- something most of us are simply not equipped, educated, or prepared to do. Some may prove toxic to aquatic and other animal life if consumed, steeped, or otherwise utilized in the aquarium. 

I can't tell you if that cool seed pod you found on holiday in Ibiza or your hiking trip in The Appalachians is going to nuke your Geophagus tank. I can only tell you how we'd approach it: Try to research what you can (there's this crazy cool site, g-o-o-g-l-e, and they have all sorts of information you can look up!), and...experiment with what you consider "expendable" (gulp- I cringe even saying that...) fishes in a reasonably controlled setting. Yeah, "experiment." Risk. Chance. It's not for everyone, but if you want to use "any old seed pod" or leaf, you'll need to experiment  for yourself to know for sure. 

I can tell you that very single botanical item which we offer has been tested- and fairly extensively- in our own aquariums, and in those of some of our friends- with our own precious fishes. It's the best way, IMHO.  We didn't just wake up one day and decide to create a business because we found some cool acorns in a tree down the street. We spent years playing with this stuff. And guess what? We've killed a few fishes- very few- along the way. But we have killed some. And it wasn't just because the botanicals used were somehow "poisonous"...it was usually because we pushed it, in terms of numbers of stuff added, using the materials without preparing, or just added too much too quickly. Even with "safe" stuff, as we've discussed many times here- you can push too hard too fast, and create potentially tragic outcomes for your aquariums. 

You have to prep, add slowly, and observe. We say this over and over to the point where you're probably sick of hearing it- but we'll keep saying it. No matter what you use, where you obtain it from- or what anyone- even myself- says. Every aquarium, every fish, every situation is different, and the possible outcomes are always subject to lots of variables. Natural materials can sometimes have unpredictable results. It's as simple as that. Anytime you add anything to your closed aquatic environment, "stuff" can happen. It's reality, as you know. Some fishes, like Apistos, are very sensitive to changes in their environment, and even with "safe" botanicals, you need to go slowly when adding them to an established aquarium.

Now, after a while, like anything else, you sort of get a "feel" for what can and cannot work. You'll look at a seed pods or whatever and have a sort of hunch, test them, and be very pleasantly surprised. Other times, you'll be shocked that the seemingly innocuous leaves you just added to your test tank have the fishes gasping at the surface. You just can't be sure until you test it yourself. 

Or, of course, you can get your botanical stuff from us or some other reputable source and have a little peace of mind, knowing that we at least use the stuff regularly in our own tanks after a lot of testing. I've even seen a few  Tannin "knock offs" pop up online lately, and that's cool. Check them out, for sure. Although I sometimes can't help but wonder, based on many of their "parallel" offerings, if all they did was try to source some of the stuff we offer and simply sell it at a lower price or whatever.

Like, we did the risky groundwork, and they figured it was all safe, lol.

Well, I suppose I can't blame them for adopting this "strategy." Yet I can't help but wonder...The reality is that just dumping "any old leaf or pod" into your aquarium carries some risk to it, and that cool decorative gourd you saw at the craft store, for example, may or may not be coated, varnished, or otherwise chemically preserved with material that can easily wipe out your tank. A "bargain" is no "bargain" when your precious fish are lying dead at the bottom of your tank.

I suppose it's in our hobbyist "DNA" to want to find shortcuts, "hacks", workarounds...whatever. And that's fine. If you accept the potential risks that go with it.

There's a reason why we offer what we do, and why we obtain our botanicals from the people we do. It's why we aren't rolling out new things every single day. It takes time to source, test, and observe them in use. We test them extensively with our fishes before we'd ever think of making them available for yours. We know how they are collected and handled. We've gotten to know our global suppliers personally, which is awesome!  It took a few years. We know what to expect from them. And yeah, you might find find stuff cheaper, but I don't know for sure if you can find it safer, or backed up by lots of testing and free information on its use and preparation.

That being said, if you're fortunate enough to have a nice oak tree or whatever near by, go for it- test those leaves and if they are not harmful, use them in your aquariums! Chances are, it's totally fine. This is the fun part of playing with botanicals! There is a lot of DIY potential here. But you have to take the risk. 

(White Oak. Pic by Msact, used under CC BY-S.A. 3.0)

And it's worth it to me, when you can create an amazing, natural-looking-and-performing habitat for your fishes. You may just want to wait until someone else has done the groundwork, and that's totally cool, too.

So, if you see that cool seed pod, leaf, or piece of wood on your next hike, and think to yourself, "Gee, that would look killer in my Apisto tank!"- Go for it...but only after you weigh the risks, prepare the item for use, and test it carefully.

It's a very enjoyable, alluring, and fascinating part of the hobby, if you take the proper steps to minimize risk.

Stay adventurous. Stay curious. Stay excited.

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


5 Responses

Scott Fellman
Scott Fellman

March 22, 2021

Hi Chaminda,

Like any leaves, Adding guava to your tank will perhaps color the water, as well as impart some tannins and other compounds. And of course, they will recruit biofilms on their surfaces. The Mulberry leaves are really more of a direct feed for shrimp than anything else. Of course, as stated above, any leaf potentially imparts a variety of compounds into the water. I’m not sure what the Indian Coral Leaf plant is; you might need to research that one!


Scott Fellman
Scott Fellman

March 22, 2021

Hi Chaminda,

Like any leaves, Adding guava to your tank will perhaps color the water, as well as impart some tannins and other compounds. And of course, they will recruit biofilms on their surfaces. The Mulberry leaves are really more of a direct feed for shrimp than anything else. Of course, as stated above, any leaf potentially imparts a variety of compounds into the water. I’m not sure what the Indian Coral Leaf plant is; you might need to research that one!


Chaminda  Fernando
Chaminda Fernando

March 21, 2021

Hi Scott,
Thank you for the fascinating article! I would like to know if you have any knowledge to share about the effects of using below leaves on fish or shrimp tanks.
Mulberry leaves, guava leaves and Indian coral plant leaves? I have heard that these leaves are being used to condition the water but not quite sure about it. If you can share your knowledge that would be wonderful

Scott Fellman
Scott Fellman

April 14, 2017

Thanks for the kind words, Todd! Always a pleasure to hear from you. I think, as you do, that just sort of “keeping it real” and sharing our passions for this stuff will really help as many hobbyists as possible discover new and exciting ways to keep our fishes. Can’t wait to see what you do in the blackwater/botanical area!

Thanks for the kind words. They mean a lot!



Todd Lachmann
Todd Lachmann

April 13, 2017

An enjoyable, fascinating and informative read as usual Scott, really looking forward to starting this new journey in the Fish Keeping Hobby.
In my experience you mostly get what you pay for, and though a big DIY guy give credit where credit is due to those in the know. I go out of my way to support those who are honest, transparent and ethical in their business practices and like Unique Corals I’m sure to be a happy customer here with Tannin Aquatics. Thanks my friend, for doing what you do and how you go about it.

Cheers, Todd

Leave a comment