Green and brown- a good combo!

One of the things we're seeing more an more of these days (besides super cool aquaecapes, lots of spawnings, and some really enthusiasts aquarists) are PLANTED BLACKWATER TANKS!

Or, more properly stated- "blackwater tanks in which aquatic plants are flourishing." Now, in all fairness, we have tended to utilize wood, botanicals, and leaves- essentially "hardscape" materials- as the primary components of our botanicals-oriented systems, but this is changing daily. We also tend to work with marginal and terrestrial plants above and near the water surface, as well.

And we are seeing some cool experiments with "botanical mulch" and alternative substrates with plants as well...

For the longest time, however, it seemed as though the aquarium world has had this "issue" about keeping plants in aquariums with blackwater. It was simply "it doesn't work." And of course, being the stubborn type, I had to figure out why this thought took hold.

Now, not being a plant expert, I don't even pretend to know 1/100th of what some of you know, and there are many experts out there who will be able to "school me" on this topic...but I can't help but think that the initial hesitation many hobbyists had about keeping plants in blackwater tanks was that there was a perception that somehow, blackwater was "bad" for them. Like a "mental block" sort of thing...we've seen this before, haven't we?

That's obviously a bit of an over-simplification, but I think it's a classic example of the way misconceptions seem to spread in the hobby. Somewhere along the line, someone threw in some high-light-loving plants into a "tinted" tank, they failed to thrive, jumped on a forum to post his/her "findings", and it went on from there...I'll even bet they went through a "checklist" and "rationalization" in their head: "Okay..I used the same lighting I did in my clear-water tank, the same fertilizers, and the same maintenance routines...they just barely grew...Plants can't grow in blackwater tanks."

Hmm...did he say, "...the same lighting?" Yeah, he did.

Well, there is something, right?

It's a known fact that light doesn't penetrate as effectively in the tinted water of blackwater environments. We've talked about this before. That's ONE of the reasons you don't see a lot of algae in many blackwater systems. And floating plants, of course, tend to do well-because you don't really have the "light penetration factor" influencing them as much as say, rooted plants. Light penetration is a limiting factor, other things being "more-or-less" equal, right? 

But they're not.

I mean, to some extent, blackwater may be described as more "nutrient poor", and having much lower ionic concentrations of calcium, magnesium, sodium, and potassium than clearwater environments.

You overcome this by...fertilizing. Just like you do in a "clearwater" system. You'll probably have to adjust your doses to compensate for the near lack of the above-referenced major ions, but it's pretty much that simple, in my experience. You'll use more fertilizers. And if you're growing plants that rely on rich substrates, like Cryptocoryne, I've found that you don't have to do all that much differently than you do in a clearwater tank.

So, really, the "keys to success" with plants in blackwater systems are essentially the same as in clear-water aquariums. You just need to do a bit more: Ramp up the light and fertilizers to compensate for what could be lacking. Verify through testing. You should investigate hardness, too. Not every plant can adapt as well to our soft water conditions. Other than that, I personally have not really experienced any other issues with keeping plants effectively in blackwater aquariums, as many of you have observed as well.


Now, I'll also be the first to tell you that many of the habitats we love, like Amazonian Igapo (inundated forest floors) and such don't have aquatic plants to any great extent. The plants you typically see in the cool pics we feature are terrestrial plants and grasses that are goring out of the water (or trying to, anyways).


There are, of course, plenty of blackwater habitats in nature where known aquatic plants grow and thrive, like in Southeast Asia, where you see lots of Crptyocorynes and other plants which even favor blackwater habitats, growing both submerged and emersed.

Yet, the mindset is slow to change in many in the "mainstream hobby", and the impression is only now breaking from "You can't" to "Oh, look- you CAN!"

This is another one of those cases where there is some validity to the claim- Yeah, you can't expect plants to thrive in blackwater under the same regimens that they do in clear water. You need to compensate, test, and adjust. It's what planted tank enthusiasts do, anyways! However, somewhere along the line, along with "Tannins are bad!" and "Blackwater tanks are dirty", the assumption that".. you can't keep plants in a blackwater aquarium!" took hold. 

And I think it kind of held some people back for a while.

Like many things we do in the hobby, a "mental shift" and an open mind are typically what are required to overcome a long-held assumption. Oh, and a shitload of planted blackwater tank pics!

As always, we urge you to push a little harder. Go a little deeper. Ask a few more questions. Try a few more experiments...before you conclude that anything we talk about here is an "absolute." The answers are out there, and in their case, they're right in that little corner of nature, where the green plants are thriving in the brown water.

Stay open minded. Stay skeptical. Stay relentless.

And Stay Wet.

Scott Fellman

Tannin Aquatics


Scott Fellman
Scott Fellman


1 Response

Michael Crawford
Michael Crawford

May 26, 2020

Awesome piece!
I came to find this after a thought I had this afternoon… I’ve never had algae in a Blackwater tank. I’ve grown crypts, lillies and mosses well in them.
Surely leaf litter and botanicals are as beneficial to plants as they are to fish?
So now the leaf litter has been added to two of my scapes!

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