A forest in the dark? Thoughts on planted blackwater aquariums.

I never portray myself as an expert on aquatic plants. In fact, I never portray myself as "knowledgable" about 'em. 

Oh, sure, I love aquatic plants and the look and benefits they bring, it's just that my primary focus has always been on the hardscape and fishes, and plants have sort of fulfilled an undeserved "supporting" role in my recent aquariums. Obviously, most of my recent freshwater aquarium efforts have been dominated by stuff like wood, leaves, and seed pods. Items which lower the pH and contribute to that "tint" which you hear me ranting on about non-stop.

And the key here is "tint"- because that's been the big hesitancy for a lot of hobbyists who want to play with plants in a blackwater system. The concern of many is that the tint imparted by the tannins will inhibit the growth and/or coloration of their plants. I'm not aware of any specific issues related to the tannin in the water inhibiting plant growth. Although many natural blackwater environments have few aquatic plants and little algae, so there's obviously more to it.

I do know of a number hobbyists who played with Cryptocoryne in blackwater systems for a long time, with a few caveats, such as keeping the carbonate hardness low to non-existent (hey, RO/DI, right?), pH low, nutrients limited, and lighting not excessively bright.  Sounds like a typical blackwater aquarium to me! The species were a bit more "rare", yet are available in the hobby when you look: C. pallidinervia, C. yujii, C. zonata, C. longicaudata. And there are dozens more. Some are "obligate" low light plants, and They don't really like highly mineralized conditions (i.e.; high level of nutrients in the solution).

Interesting to me is the use of low pH substrates and leaf litter in their culture ( a lot of the blackwater Crypt. "players" use Beech, etc. in a ground up form, almost like a mulch of sorts...cool). Interestingly enough, many of the so-called "blackwater Crypts" also tend to "melt" if they are in soils that are too nutrient rich...A lot to take in here.

Okay, those crazy hardcore plant people love making stuff complicated, don't they? I mean, they're pretty brilliant, but most of the stuff they talk about is a bit more in depth than I care to go. That stuff kind of "buzz-killed" the whole thing for me...just a bit too "horticultural", ya' know? So for my "trials" in my latest office tank, I it did it the old-fashioned, hardcore fish-geek way: I just obtained some cuttings of plants I liked from a friend, Luis Navarro (who happens to be one of the best planted guys in the game) and went for it.

The real intention of my plant experiment was to utilize a plant that would grow out of the water. He recommended the uber-cool Polygonum sp. "Kawagoeanum", and I couldn't be happier. 

It's a very interesting (okay, it's Asian...but it looks kind of "Amazonian" to me) plant that has amazing colorful leaves and tons of roots that drive those competition-oriented "Nature Aquarium"-types crazy, because they look "messy" (as opposed to their neatly-ordered tanks filled with very "natural" underwater waterfalls, fantasy forests, and floating moss "trees"...yeah, okay...)! And it turns out, that with some nice LED light and my basic, non-nutrient-infused Carib-Sea "Torpedo Beach" substrate covered in assorted leaf litter, this easy plant is growing like...well- like a weed...literally, because I just let it do it's thing. Darkly tinted water notwithstanding, it's doing great.

As stated above, I'm absolutely no plant expert, nor do I claim to have some magic formula or procedure to get plants to grow. Really, I think it's a combination of dumb luck, good source plants, and consistent environmental conditions. However, over the years, I've played with plants like Crypts, Cabomba, Amazon and Pygmy Swords in blackwater tanks, and enjoyed similar sucesses...

What's it all mean? I think it means that most plants are adaptable.

I think hardcore plant people are a bit concerned about many plants in blackwater tanks because they (correctly) are under the impression that blackwater will cut down on the light that gets to the plants, as touched on above. Well, sure, it's tinted, right? However, I think the popular misconception about blackwater (and this is a hunch I have based on talking to a lot of hobbyists who think my obsession with the stuff is weird) is that it's always "murky" somehow...like the tint and "murkiness" go hand in hand.

I, of course, disagree completely with that misconception, and my tank water is as clear as glass, from a visability/turbidity standpoint. It's just...brown. Oh, and my tank grows plants. And I'm not the only person who is doing this...In fact, there are tons and tons of people doing this, with full-on planted tanks that would rival any of those "Fairy and Wizard Fantasy 'scapes" that you see in the big international aquascaping competitions. It's just that I think a lot of people don't talk about it, because blackwater tanks in general have been sort of pushed into a "subculture" status for a long time. 

I think it's time to show off some planted blackwater aquariums! Like our hardscape, it's a totally different aesthetic- an aesthetic that embraces some algae, biofilm, "disorder"- stuff that a lot of aquarists don't like. 

And I get it.

However, for those of you that were itching to try some plants in your blackwater tanks to go with your botanicals...I say, go for it!

Sure, you could use plants that are more closely aligned with the geographic region you're trying to represent in your tank, but I think you can allow yourself some "artistic liberties" to make things less rigid, and more enjoyable (you know, like an Asian plant in your "South American-inspired" tank...). Purists will hate you. Counter-cutlure hobbyists will love you. And everyone will benefit from the information you share.

Todays' disjointed dissertation on something that you may have already tried...

Enjoy your "tint." Stay experimental. Stay adventurous.

And Stay Wet!


Scott Fellman

Tannin Aquatics

Scott Fellman
Scott Fellman


4 Responses

Scott Fellman
Scott Fellman

October 25, 2018

Hi Natalia!

Sounds like a cool tank..I can’t help but think of the “usual suspects”- Cryptocoryne, Bucephalandra, perhaps some moss and a few floating plants. See our Facebook page for a pic of Johnny Ciotti’s Borneo themed tank! He also has Rotala in there that is really thriving! As far as botanicals- I like stuff like Rio Fruta, Ceu Fruta, Savu Pods, Yellow Mangrove Leaves, Guava Leaves, Fishtail Palm Stems, Coco Curls, Flor Rio…stuff like that!

Would love to see the finished product! Enjoy and good luck!


Natalia A Podunavac
Natalia A Podunavac

October 24, 2018

I will be setting up a 50 gallon “frag”/lowboy tank as a blackwater tank with a pH near 5, for some kuhlis (Pangio semicincta, oblonga and myersi), and two large schools of Boraras brigittae and Sundadanio axelrodi.

Would love to know any recommendations on plants that you have had success with in a blackwater setup and related botanicals, I would like to stay regional, but I can’t say no to a plant I like.

Scott Fellman
Scott Fellman

October 17, 2018

Glad to hear that, David! I think we’re finding that not only are there a lot of plants founding blackwater, but that we are not as a hobby putting two and two together and realizing that we can keep them in these conditions if we provide the overall environment for them!

David fieldman
David fieldman

October 16, 2018

Hi Scott I have a fully planted Blackwater tank that is doing great for last three years had a lot comments say it’s wrong but plants are doing great

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