Bottoms up!

I have an obsession with substrates. 

I'm not sure what it is, but I love them. Sands, gravels, soils...rubble...even leaves...just about anything you would want to use on the bottom of your aquarium.

Im facilitated by the impact of materials on the aquatic environment in an aquarium...I love the idea of using different, potentially "unconventional" materials in our aquatic microcosms. The potential for all sorts of cool benefits exists; Of course, not without some potential problems along the way (like CO2 issues, aerobic pockets, etc.), but it's a fascinating obsession for me. And of course, this obsession has led us to offer products like "Fundo Tropical" and such to create more "functional" botanical-oriented substrates. It's a natural extension of our offering, and my strange obsession!

It got me thinking, of course, about what the best substrates are for our blackwater, botanical-style aquariums. I really enjoy reading about "active substrates" with the talented planted tank and shrimp crowd. There's a lot to like there- most significantly, the hobbyists aren't just using the substrate as some sort of "afterthought"- some bottom cover to complete the look. Rather, they're incorporating it as an important, functional part of their microcosm...this is really cool!

I think we as "tinters' have a lot in common with these hobbyists, and we're often seeking to create aquariums in which the botanical are not just there for their sexy looks; rather, they're used to impart some valuable compounds and foster processes, such as foraging and food "cultivation" areas, potentially biological filtration (via fungal and biofilm growth), and perhaps other benefits yet to be realized. 

I think we need to investigate the potential benefits of using some of the active substrate materials marketed by many manufacturers now. It's interesting to see substrate materials which can lower GH and pH over time. They work great for plants, as we know, and I think they will also aid in maintaining the environmental parameters that we are interested in as well, although I think the greater impact is on the plants, these materials by virtue of their composition DO help the overall pH of the system, correct? (yeah, I'm asking a sort of rhetorical question, lol) They definitely impact the hardness, so there is a definite effect there...

I'm curious about any sort of "synergistic effects" of using "active substrate" materials in conjunction with botanicals to create even richer and more stable blackwater environments. I've read a few "over-my-head" scholarly articles on some of the geological materials of the Amazonia region, which comprise the soils in some of the flooded forests and streams that we obsess over, and I'm curious as to which of the commercially-available products most accurately represent the composition of these native soils and substrates.

You can probably see where I'm getting at, right? I think that it would be fun to see just how accurately  (from a "functional" perspective, at least) we could represent as many aspects of the wild habitats in our aquariums as possible, so that there might actually be a real "method" to our madness. That being said, the other question would be to investigate if there is an advantage to utilizing sands, gravels, etc.- chemically neutral or even somewhat "buffering" substrates- in our systems. I think we also need bring in our vivarium friends, who have extensive knowledge of incorporating terrestrial materials in their displays...they are well-versed on the benefits of different materials, too!

I was playing around with substrate composition lately when setting up my brackish water aquarium, in an attempt to replicate somewhat the soils/muds that are common in mangrove habitats.

Interestingly, I'm not attempting to "root" mangroves in the tank initially. Rather, I want to incorporate some more salt tolerant (sg 1.003) plants, like Cryptocoryne ciliata, in this substrate. And I'm also looking to see what other positive environmental impacts a sort of "active substrate" can create in a brackish aquarium. Perhaps we can incorporate some sand-dwelling organisms to help "work" the substrate, as in a reef aquairum...Anyways, I'm sure there will be some denitrification, but there might also be some potential for negative effects (like aerobic pockets, etc.) if plants are not present. However, I'm very, very interested in the overall impact of rich substrate materials in a brackish tank, and I forged ahead regardless (Someone has to be the fool, right? May as well be moi)!

We'll have much more on this tank in future installments of "The Tint", but I felt at least telling you what I was thinking as respects to substrates with this tank is relevant to our discussion here! Besides, playing on highly speculative, unsubstantiated "hunches" about stuff is what I'm all about! (heh, heh...)

So...I, I"m certain- that there is a lot of interesting stuff we as blackwater, botanical enthusiasts can look into in the substrate realm. I'd love to see more discussion and ideation from those of you who are far, far better versed than I in this area. I will kick off such a discussion on our Facebook page soon, because I'd like to see more of you playing with this! Some of you already are, and have reported both good and bad effects...or at the least, pushed the limits a bit and have developed your own sets of "protocols" in regards to how to manage these setups.

It's a real wide-open field for serious aquarium research. A lot has been done in the reef world on deep sand beds and such, and I don't find much on the idea of creating "functional" substrates much in freshwater, outside of the aforementioned planted and shrimp "disciplines." What we're talking about would be to certainly take advantage of the things learned by our shrimp/plant friends, but to also investigate other benefits of "active" or "functional" substrates. 

Who's in? 

Stay excited. Stay adventurous. Stay curious. Stay creative!

And Stay Wet.


Scott Fellman

Tannin Aquatics 


Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

May 25, 2017

As always, Garrett- SPOT ON! “Crashes” and such are incredibly rare…and generally due to other factors besides something like this…a “coach” as a result of this type of error would take a while to manifest- there would be clues. Overnight anomalous disasters are often weeks- if not months- in the making…commons sense, water testing…and good old observation can head off most of ’em. Great information!



May 22, 2017

Aerobic/anaerobic pockets are the boogeymen of the aquarium world. You can’t drop the idea of a DSB (freshwater or saltwater) without a dozen people warning you of total tank annihilation from a roiling sulfuric cloud of death. And it’s true – just like you run the risk of getting hit by a car every time you step out your front door.

I did a ton of research on freshwater DSBs, dirted tanks, and organic substrates while I was planning my biotope aquarium – we’re talking dozens of hours, scouring forums until I needed Google Translate. Do you know how many confirmed tank die-offs from gas bubble releases I found that were first-hand observations – not “I heard about a guy”? Two. TWO. And both were in tanks that had been running for over 5 and 10 years respectively with admitted little-to-no substrate maintenance, when a large fish decided to go digging for some reason.

The truth is, if you maintain your substrate – either aerating it with chopsticks weekly, or using rooted plants and burrowing inverts like blackworms or MTS – you will never have to worry about it. Heck, even just running your gravel vac lightly above the substrate surface will suck up most of the air bubbles.

My substrate is a mix of coconut fiber, play sand, leaf and veggie mulch, snail poo, dead baby snails and gravel. I have some hairgrass and an anubias planted, and there are about a dozen MTS. In the beginning I would regularly get small bubbles coming up every once in a while as the organic matter decomposed, but now it’s only when the trumpet snails blunder into them. Ammonia, nitrates and nitrites are all normal. The best part is that before I set up the hardscape and leaf litter, it looked exactly like the handful of photos and videos that I could find of Amazonian blackwater and clearwater stream substrates – fine, neutral-to-reddish sand with a sprinkling of organic matter.

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