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Just what are the real benefits of Catappa leaves, anyways?

Tannin Aquatics

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I sound like a "broken record" (wow, that's a really outdated expression, huh?), blabbing on and on daily about the virtues of Catappa leaves, wood, and aquatic botanicals.


really get excited about leaves! Specifically, Catappa leaves!

Catappa leaves have been used by fish geeks for a number of years, especially Betta enthusiasts in Southeast Asia, and there has been a lot written on them. Regardless, a lot of the stuff written about the virtues of using leaves is often couched in some nebulous sales-y sounding gobbledygook, sprinkled with lots of expressions likes "makes the environment appropriate" or "corrects environmental problems" and (my favorite) "conditions water",  by people like me who make a living selling them. Yeah, a bit self-serving, I admit...but how else can we get you into the idea of using what we sell? :)

I decided that my little piece here will just deal with what we know, sans the ridiculous hyperbole. Here's the deal: Catappa leaves (aka "Indian Almond leaves") come from the Terminalia catappa tree. These trees are found throughout the tropical world, in Asia, Africa, and Australia. They can reach a height of over 100 feet tall, so we're not talking about a wimpy little bush here! 

The big benefits of the Catappa tree to us aquarium geeks, of course, are the bark and particularly, the leaves, which contain a host of interesting chemicals. The leaves contain several flavonoids, like kaempferol and quercetin, a number of tannins, like punicalin and punicalagin, and a suite of saponins and phytosterols. Extracts of T. catappa have shown some effectiveness against some bacteria, specifically, Plasmodium, and some parasites as well. 

When Indian almond leaves are subjected to degradation in water, humic substances are formed, which, in turn, lower the pH of the water. The tannins are what color the water the beautiful brownish color that we geek out about so much around here at Tannin Aquatics!

There is also anecdotal evidence and theories that the tannins in Catappa leaves are able to reduce the toxicity of heavy metals in aquarium water, essentially binding them up or chelating them- a most interesting benefit for the urban fish keeper, I might add. As a curious side note, blackwater streams and rivers are acidic, resulting in an aluminum concentration greater than that of "white waters", which have a more neutral pH

"Okay, Scott. That sounds very scholarly, but what exactly are those things and what can they do for my shrimp?"

First off, I admit freely that I'm no scientist. I'm a hobbyist with a slightly higher interest in aquarium science than the typical human, and yeah, I had my share of biology and chemistry in college. That being said, I'll share with you what I know in concise, hopefully intelligible language!

Well, lets start with the flavonoids. Flavonoids have been shown to have direct and synergistic antibacterial activity (with antibiotics) and the ability to suppress bacterial virulence factors in a number of research studies. They may also act as chemical "messengers", physiological regulators, and "cell cycle inhibitors", which bodes well for their use as a prophylactic. Kaempferol, a noted flavonoid,  is thought to have anti-inflammatory and antioxidant properties. Hmm...could that be why Betta fanciers used them for so many years after fighting their fishes?

Saponins can be used to enhance penetration of macromolecules, like proteins, into cell membranes. Some are used in vaccines to help stimulate immune responses, so you can see some potential benefits here as well.

Phytosterols are interesting for their alleged capacity to reduce cholesterol in humans, but the benefits are probably non-existent for fishes, especially as it pertains to Catappa leaves in the aquarium! I mention them merely because fishy authors touting the benefits of Catappa leaves love to throw them out there. 

Punicalagins act as antioxidants and are the major component responsible for the antioxidant health benefits of fruits, such as pomegranates (You know, the "wonderful," yet really messy fruit that I always hated as a kid...). They are water soluble and have high bioavailability, so it makes sense that they are of benefit to fishes!

A cool study in Thailand with Tilapia concluded  that Catappa extract was useful at eradicating the nasty exoparasite, Trichodina, and the growth of a couple of strains of Aeromonas hydrophila was also inhibited by dosing Catappa leaf extract at a concentration of 0.5 mg/ml and up. In addition, this solution was shown to reduce the fungal infection in Tilapia eggs. 


Well, that sounds pretty cool! And it's all about fishes- not shrimps.

Only problem with the findings from the study is- and I'll be the first to admit this- most of us don't have the equipment/capability to easily determine mg/l of Catappa leaf extract is dissolved in water, so we may have to rely on the completely anecdotally-derived "recommended" number of leaves per gallon as determined by long-time users of the leaves. Meaning, we estimate based on our gut and the results we're getting...

So the "generally accepted" dose for these leaves is subjective, at best. That's typically like 1-2 large leaves (we're talking like 5" plus) for every 15 gallons (approximately)...there is no real "rule of thumb", other than recommendations derived from users over the years- and of course, like so many things in this hobby, if you ask 10 aquarists you'll probably receive 10 different answers.

Nonetheless, the leaves do have some science-backed therapeutic capabilities, as touched on briefly above, and their usefulness in helping hobbyists to safely replicate the conditions of blackwater environments in their aquarium is widely known in the hobby. These streams and rivers are fascinating subjects for recreating in our aquaria!

A blackwater stream or river flows through forested swamps, wetlands, and flooded fields. As the vegetation optioned in these features decays, the tannins bound up in these materials are released into the water, making it transparent, acidic, and darkly stained, looking like coffee or tea!

(RIP Takauhi Amano- your brilliant underwater Amazon pics will inspire forever...)

If you're trying to mimic conditions of  blackwater streams and rivers, Catappa leaves can certainly help, as we've repeatedly discussed on these pages. The breakdown of these leaves in closed aquarium systems mirrors what happens in nature, and offers many possible benefits for fishes that come from waters that are soft and acidic.

 Blackwater rivers and streams have different chemical composition from "whitewater" environments, which has lead to the formation of flora and fauna that differs significantly from what are found in other types of waters. One study showed that blackwater rivers have large numbers of organisms like rotifers, but fewer crustaceans and mites. You won't find a snails to any great extent in blackwater systems, because it is difficult for them to build their shells in these calcium-poor environments. 

Sodium, magnesium, potassium and calcium are found in much lower concentrations in blackwater systems than in other types of water, and with minimal amounts of dissolved ions, the water has much lower conductivity than you'd see in a "whitewater" system. Blackwater rivers like the Rio Negro are incredibly high in fish biodiversity, and it's estimated that they are home to over 700 known species, with around 100 being endemic to this river environment!

The potential health benefits for fishes residing in carefully-controlled "blackwater" conditions are numerous, ranging from greater disease resistance to increased spawning activity, and, as documented in several studies, higher-yielding hatches with less incidence of fungal outbreaks in egg clutches.

Again, most of the scientific studies I located about blackwater have to do with fishes; what we read about leaves and shrimp is typically from hobbyists who utilize leaves in one form or another in their work. However, it seems to me that the use of Catappa and other leaves among shrimp fans seems to be both accepted and common, with the main concern expressed by shrimp fanciers being stability of their aquatic environments.

So, all pretty cool stuff!

I hope this little meander about some of the real benefits of Catappa leaves and the blackwater environments they can help simulate will encourage you to do a little personal experimentation with them. 

With quality Catappa leaves readily available, and the documented benefits they offer, there's never been a better time to enjoy "the tint!"

Stay interested. Stay curious.

And stay wet.

Scott Fellman

Tannin Aquatics

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thanks for the good material.


You're welcome. It's fun to share ideas. To question. To ponder. Even to tease once in a while and laugh at ourselves. And I learn a lot in the process from some pretty talented people! It's interesting to ponder some of the things that we sort of take for granted in the hobby- to look at them from different, sometimes even provocative- angles! Enjoy the sharing!

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I really enjoy the conversational style of your writings. :)


You mentioned "fewer crustaceans ...because it is difficult for them to build their shells in these calcium-poor environments."


Does this mean the tannins bind with calcium in the water?


Thanks for the kind words!


Very good question, and one for which I am personally still trying to explore myself.


Quite honest, there is a bit of an apparent disconnect, in my opinion, between the composition of blackwater rivers and such, and the shrimp world's use of tannin-inducing products. Wow! A vendor shooting himself in the foot and sabotaging his own market?


Well, not exactly- but it keeps me curious. And this is why I don't come in and say "My stuff is the ultimate for all shrimp!"


​I'm a realist. I think the botanicals are useful for shrimp. But there needs to be some understanding about exactly what shrimp need, and what shrimp fanciers are trying to accomplish with natural products and such in their aquariums!


Now, I believe that the tannins are beneficial to crustaceans such as shrimp, as are the substances found in these types of environments, as outlined in the piece. However, the typical blackwater river is not as high in calcium ions as a "whitewater" environment. In one study I found, the Amazon (a "whitewater" river) had a calcium content of roughly 7.2mg/L, versus the Rio Negro (the prototypical "blackwater" river) had a calcium content of approximately 0.212mg/L !!! The pH of a typical "blackwater" river is far more acidic than a "whitewater" river. So what does this mean to a shrimp fancier? Well, if calcium is really important, as are the products produced by decomposing leaves, botanicals, etc., supplementation is probably necessary! Hence the "Mineral Stones" we use.


Another thought: Blackwaters tend to have very little in the way of copper, versus a "whitewater" environment (we're still talking trace amounts. of course).


Calcium is super important, isn't it? This is why most shrimp feeds contain calcium and iodine, as the shrimp require them for proper molting and shell development. And of course, as we know, different shrimp come from different environments in nature, and may be adapted to different conditions. 


Bees, for example, come from creeks in Southern China with soft, clean water with a pH range of roughly 5.5-6.8, and a KH between 0-2, a GH from roughly 3-6, and low TDS.


The use of leaves and even our aquatic botanicals in a shrimp aquarium would be for a supplemental food source, as well as for some environmental enrichment. As discussed in other threads, shrimp keepers are rightfully concerned about not going overboard with anything in their environments, specifically, materials that can decompose and potentially affect the cleanliness of the water.  A lot to consider here.


We recommend the judicious use of our botanicals, especially because many shrimp are kept in small tanks. You simply don't want to go crazy and add a ton of them into the shrimp tanks you maintain. There is still much room for experimentation here, and it's pretty interesting! For years, various manufacturers and vendors have offered all sorts of leaves, and cholla wood, etc. for use as food in shrimp aquariums, and fanciers have used them without incident for a long time. Obviously, these materials contribute something to the environment as they decompose. They are used widely in the shrimp world, so I'm not too concerned about hobbyists mis-applying botanicals. You just have to go slowly.


So much interesting stuff here; and not being a scientist, I can't give you every single angle on this, but I am interested in the interactions of botanicals in the shrimp aquarium. I hope some members more learned of water chemistry could chime in here. As mentioned (re; Bees) some shrimp come from more acidic, soft water environments, and the aquatic botanicals would be well suited for them. Most important, as we all know, is water quality and environmental stability.


I'm probably all over the place, but this is interesting stuff!





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