Using Oak Leaves and Twigs in Our Aquariums: The Case for Generic Tropicals — A Guest Post by Scott Fellman

The following is a guest post from Scott Fellman, founder of The Tint Blog and one of the most influential voices in the Botanical Method Aquarium space, covering our favorite generic tropical, The Oak Tree. Scott has spent over a decade documenting the ecological processes that unfold when natural materials meet aquarium water, and his thinking has shaped how a lot of us approach this methodology. In this piece, he makes a case I find hard to argue with — that Live Oak, as unassuming as it is, might be the single most useful botanical material available to us. I'll let him take it from here.

As some of you know, after all of these years following my rants and theories here in "The Tint", I have a healthy obsession with utilizing leaves and twigs in my aquariums.

Can You Use Oak Leaves in a Botanical Method Aquarium?

Let's talk about those leaves first!

If you ask me what my absolute fave leaf is — despite having sampled and tested some of the most exotic leaves in the world in my aquariums — my hands-down favorite is the decidedly un-exotic Live Oak leaf! Yeah, LIVE OAK! Possibly the least sexy botanical material available, but, IMHO, one of the best and most versatile!

Oak belongs to the genus Quercus, of the beech family (Fagaceae), with almost 500 species. A large and diverse genus, which, according to Wikipedia, "is native to the Northern Hemisphere, and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. North America has the largest number of oak species, with approximately 160 species in Mexico of which 109 are endemic and about 90 in the United States. The second greatest area of oak diversity is China, with approximately 100 species."

So, in plain English, Oak is found across a broad swath of the planet, making it one of the most readily available and accessible botanical resources for hobbyists worldwide. The fact that you can collect them yourself if you can source them is a huge plus!

— Thinking about collecting your own? See our How to Collect Leaf Litter Safely guide first.

Part of the reason I love Live Oak leaves so much is that, not only are they a great "aesthetic" substitute for any number of tropical leaves, and easy to come by for many of us — they are biologically and chemically beneficial in fostering the type of ecological conditions that us botanical-method aquarists obsess over!

When oak trees shed their leaves, they have by and large depleted their share of calcium, magnesium, and potassium-base elements which not only tend to make aquarium water more alkaline, but make it more difficult to manipulate chemically without techniques like reverse osmosis or deionization. On the other hand, oak leaves produce significant quantities of tannic acids, which, as we know, are useful to us as botanical method aquarium geeks!

The amount of "ash" content (in the form of calcium and magnesium oxides) of oak leaves is something like 30% less than in other types of leaves. Ecologists associate this low content of these compounds with a lower rate of decay, induced by various types of soil biota (millipedes, etc.). In short, they just don't taste as good to many of the small creatures at the base of the food chain (terrestrial and aquatic) which help to physically break them down. As a result, they last longer, retaining their form and structure, contributing more to the chemistry and ecology of the aquarium water over time.

— We carry four varieties of Live Oak leaf litter: Texas Live Oak Leaf Litter, Pacific Live Oak Leaf Litter, Shingle Oak Leaf Litter, and Willow Live Oak Leaf Litter.

Can You Add Oak Twigs and Branches to an Aquarium?

And when it comes to what kind of "decorative" wood I use in my aquariums most frequently, it goes without saying that I once again typically turn to the humble Oak tree for my botanical method aquarium needs!

And of course, one immediate consideration aquarium geeks contend with when using branches of any type in their aquariums is, "How do I prepare them for aquarium use?"

Yeah, pretty much all wood and branches float like mad when you first submerge them…And they DO need some preparation because, well — they're fucking dirty!

— For a full rundown on how to prepare botanicals before adding them to your aquarium, see our Botanical Preparation Instructions.

How to Prepare Oak Wood for Aquarium Use: The Case for In Situ Curing

"Conventional Aquarium Practice" is to soak and/or boil wood for some extended period of time, not only to help "rid it of toxins" but to get it to saturate, sink, and stay down.

In theory, no problem, right?

Now, with twigs and branches, the idea of practicality comes in. Like, what type of vessel do you conduct this "preparation" in? Most of us simply don't have a freaking cauldron or big-ass kettle — let alone, a "stove" large enough upon which to boil a bunch of branches, right?

So, compromise is in order.

Soaking is not a bad thing.

In the aquarium.

I've touched on the idea of "in situ" preparation of wood, and it really does make sense with oak branches (largely because of the size issue) — and consider this:

It's pretty obvious that at least part of the reason we see a burst of new algae growth and biofilm in wood recently added to an aquarium is that there is so much "stuff" bound up in it. "Organics", like sugars, lignins, and compounds found in soils, etc. Algal and fungal spores can literally "bloom" during the initial period after submersion. It's exactly what happens in the wild aquatic habitats of the world when tree trunks and branches are covered by water.

I get it — a lot of hobbyists simply don't want to see this stuff in their display aquarium.

On the other hand, the adventurous aquarist in me can't help but wonder if we should just give the wood a thorough washing, and let this whole process play out in the aquarium, to foster this amazing biodiversity within the aquarium itself. This is the essence of the botanical method aquarium technique.

Again, this is an example of setting up an aquarium from the start to replicate both the form and function of Nature.

— New to the Botanical Method Aquarium? Our How to Set Up a Botanical Method Aquarium guide is a good place to start.

Why would you NOT do this? Especially with "self-collected" stuff like oak branches?

What would the "downsides" be? I've done this many times with no issues.

The "downsides" are, IMHO, psychological — a tension from our century-old "modern" aquarium hobby practices!

Admittedly, the experience with "in situ curing" IS a bit different.

It starts with what you see.

Yeah, you'll see a lot more biofilm, fungal growth, detritus, and perhaps even slightly hazy water. It looks kind of, well, yucky to a lot of hobbyists. When your water gets dark and cloudy, internal questions arise in your mind, like, "What have I gotten into? Will this ever clear up? Is this dangerous?"

Well, sure, healthy skepticism about an "unorthodox" approach is always good to have. And let's be clear — as with any aquarium startup, you'll want to carefully monitor the nitrogen cycle, and manage nutrient accumulations with good husbandry…

You'll have to employ a lot of patience, and yeah, I'd recommend some water testing during the "break-in" process. Testing for what? Well, I'd likely do ammonia and nitrite, for starters. "Have you done all of this testing when you tried this, Scott?"

Not always, I admit.

Why, Scott?

For one thing, it's because I'm in no rush to add fishes to brand-new aquariums. Because I typically let my aquariums develop ecologically for a long time before I add fishes to them. I've done it like this for years. And the lack of testing that I've embraced (contrary to my decades of advanced reef keeping practice, I might add) I did this out of sheer curiosity, of course! And the "cycle" time was really nothing extraordinary at all, in comparison to a "typical" hobby approach.

Really, the biggest difference between this "in-situ-curing" approach for wood versus using an external container is that any of the stuff that emerges from the wood itself will leach into, and "accumulate" in the display aquarium, and impact the water appearance, and chemistry. Although I admit, I didn't notice a significant difference in nitrate or even phosphate in new aquariums where the "curing" process was undertaken internally.

Remember, I'm a water exchange fanatic; I perform 10% water exchanges in every aquarium I maintain — every week, without fail. So there was some dilution of whatever organics were found in the water.

What Actually Leaches Out of Submerged Wood

The biggest difference I've determined by testing is often TDS. And of course, because TDS represents the "total concentration of dissolved substances" in water it can include both inorganic salts, as well as a small amount of organic matter. To me, "TDS" is always a bit of a vague thing; I mean, it can be so many different things. Regardless, when I cure "in situ", TDS readings are typically higher than in aquariums where this process isn't employed.

Do some of the other materials leached out of wood have implications for the healthy break-in and operation of your aquarium? Can you even test for everything that leaches out of newly submerged wood, other than simply labeling these compounds as "organics?"

Likely NOT, in the hobby world.

Well, lignin is one substance that you might find leaching out of wood. And there are actually lignin test kits out there for scientific work; I suppose it would be interesting and informative to test for them to see what the concentration was, although I'm not really sure what function it would perform, other than just kind of "knowing."

Just like with testing for tannins, interpreting what is "baseline" or even "okay" for lignin is something we have never really done in the hobby, right? Another supposition would be that lignin concentration might be different in a filtered aquarium than it would be in some big container of water without a filter that you might cure wood in.

The point is, there are some things that we just don't know.

Why "In Situ" Curing Works

We assume. I mean, whenever we "cure" wood externally, we almost always see lots of that "yucky" biofilm and fungal growth on the surface tissues. That's "par for the course" when terrestrial materials are submerged. And it's only "yucky" to some. Not geeks like me or you (I hope.)

The real issue that makes "in situ" curing a bit unusual is the possible "gross pollutants" that may leach out of the wood. I suppose that would be stuff like dust, dirt, maybe some small amounts of sap, surface pollutants, etc., bound up in or on the surface tissues of the wood.

I did a lot of research on this in the online forums, articles, etc, and the reasons why it's recommended that wood be "cured" outside of the display aquarium are always listed as (in no particular order): "to leach out impurities", "to leach out tannins" (What the actual FUCK?), to "let the fungal growth subside" (Blasphemy!), and "to waterlog and sink." (I'm okay with that one).

Now, other than "waterlog and sink" process, which you can accomplish in the display aquarium by simply placing a few rocks on the wood, IMHO none of the other reasons given for external curing of wood are really "non-starters" here. They're just NOT!

It's occasionally stated that boiling wood or extended soaking helps eliminate potential parasites that might be present in/on the wood. I'd hazard a guess that most wood used in aquariums doesn't have significant populations of parasites that could harm fishes, either. And again, even if there are such parasites present, if you're taking your time to add fishes (essentially keeping your aquarium "fallow" for a period of time) you're essentially denying any parasites that are present their "hosts", right?

Am I missing something here?

I don't really think so. It's just that I don't see the "stuff" that happens during the curing process as a "problem." I see it as a part of the process of establishing my aquarium's ecology.

"In situ" curing isn't a perfect, guaranteed route to accomplishing everything you want to easily, but it works! And the process and its impacts on the ecology of your aquarium is not all that different than what occurs in Nature, when you think about it.

In Nature, it is not uncommon at all for small (and large) trees to fall in the rain forest, with punishing rain and saturated ground conspiring to easily knock over anything that's not firmly rooted!

When these trees fall over, they often fall into small streams, or in the case of the várzea or igapó environments in The Amazon (the ones that I'm totally obsessed with), they fall and are ultimately submerged in the inundated forest floor when the waters return.

And of course, they immediately impact their (now) aquatic environment, fulfilling several functions.

Fallen trees provide a physical barrier or separation from currents, perhaps creating a little "dam", which accumulates leaves, sediments, and detritus — all important as food sources to a huge number of aquatic organisms.

They also provide a "substrate" for algae and biofilms to multiply on, providing places for fishes to forage among, and hide in. Many fishes, like small cichlids, will reproduce and raise their fry among these fallen tree trunks.

An entire community of aquatic life forms uses the fallen tree for many purposes. And the tree trunks, branches, and other parts of the tree will last for many years, fulfilling this important role in the aquatic ecosystems they now reside in each time the waters return.

Oak Leaves, Twigs, and Branches: Building a Botanical Method Aquarium Hardscape

So, all of this talk of prep is important…but the idea of "prep" can encompass many things. It's one of those things that we as hobbyists know to do, but we always sort of second guess ourselves about HOW to do it.

The fact is, we need to embrace SOME sort of preparation protocol for any natural materials that we add to our aquariums.

Okay, that was another of my famous detours, but a necessary one. We wrestle talking about oak leaves and twigs and branches, so why not go all in and twist around a bit?

I love creating aquariums in which the "hardscape" consists mainly of twigs and small branches. I've been sharing these kinds of aquariums with you since 2015. It's not a new concept.

Oak is the perfect "provider" of these materials, BTW. It keeps things simple and easy.

The beautiful thing about this idea is that you don't necessarily have to use 12 different varieties of branches and such to create a remarkably complex and interesting scape. Just oak!

Oak twigs and branches, and oak leaves are pretty much all you need for a sweet, functional, ecologically diverse and successful botanical method aquarium, IMHO.

— We carry two options for oak wood hardscape: Oak Twigs, Sticks & Branches for building understory and substrate structure, and Live Oak Branches for individually selected WYSIWYG pieces.

It's not just about the aesthetic, of course.

The idea is that you're creating a matrix of these materials to impart a very natural and interesting look to the aquarium. These aggregations provide fishes with hiding places, foraging areas, and spawning sites, just like they do in Nature…

Until next time.

Stay Wet.

Scott Fellman

Scott Fellman has been writing about the Botanical Method Aquarium since 2015 through his blog, The Tint. If this piece sparked something — the chemistry of fallen wood, the ecology of the igapó, the case for letting your aquarium develop slowly on its own terms — there are years of that thinking waiting for you over there. Scott publishes regularly, and the archives alone are worth an afternoon. We're grateful to have his voice here.