December 27, 2021

Why leaves make lousy "hardscape" pieces...

We're about a month out from us performing a "hard stop" on the term "botanical-style" aquarium to describe what we do, and begin substituting it with the more accurate descriptor, "botanical method" aquarium. Yet, I still find that many in the hobby tend to think of materials such as leaves as more of an "aquascaping material" as opposed to an "ecological enhancer."

Perodically, I find it necessary to reinforce some of my arguments for why we do things a certain way in this little hobby speciality. And one of the most fundamental discussions we can have on this topic is about my favorite botanical material of all- leaves. My thinking was that this it might make sense to make my case for why leaves are kind of a lousy material to use strictly for aesthetic purposes, but wonderful for ecological benefits for our aquariums.

The reality, as I have seen it, is that there is a philosophy that goes with incorporating leaves into your aquascape, much like with rocks or aquatic plants.

Yes, a philosophy.

I've noticed with botanicals- particularly the leaves that I'm so fond of- that you need to be sort of "flexible" in your thinking. and in how you embrace them in your "design", if you're incorporating individual leaves, and using them mainly for their aesthetics. They are among the most simple elements we can use to create a natural aquarium, or even for an "aquascape", if that's your orientation . However, they can also frustrate you if you don't train yourself to accept that they won't always do what you want them to do.

They will float, curl up, blow around, not stay in the orientation that we want them to, and just generally behave "the way they want" (as if they have a "desire" of their own...) .

With very few exceptions, using individual leaves to create some sort of aesthetic in your tank is simply asking for frustration. IMHO, they are best used as an aggregation of many leaves- as in leaf litter beds...much how you'd find them in Nature. They not only simply look better when used in aggregations- their ecological function is enhanced as well.

And don't forget that, once we get leaves down into our aquariums, they will start to recruit biofilms and fungal growths, slowly soften, and ultimately, decompose over a few weeks or months (depending upon the variety you're using), which alters your "aquascape" almost the minute you complete it! This is absolutely what happens in Nature, of course. Leaves are among the most transient of botanical materials.

Now, if you accept this, and incorporate this process as a part of your aquariums' ecology, as well as its evolving aesthetic- then it can get interesting! And gratifying, too!

Okay, it sounds like I'm "raining on your parade" if using leaves strictly as an aesthetic component is your thing. I'm not. I'm merely suggesting that you need to understand what you're getting into, and how they work. You need to understand why we prepare them for use in our aquariums, and how this is an advantage for the fishes that we keep.

They're just not like rocks or wood in both "behavior" and influence. The function is of paramount importance; the aesthetic is a result of the function!

Remember, leaves are an extremely ephemeral element to 'scape with, yet they can provide a surprisingly dynamic component to your design if you understand this. Because of their transient nature, they will shift position, change color, become covered in detritus, and even "morph" their shape after submergence.

All of these characteristics mean that we need to take this into consideration when incorporating them, and that we need to accept that the beautiful yellow leaf you have in the front of your aquarium today will likely fade into a golden brown, twisted and deteriorating one in a month or so. With leaves, you can look at this as a "burden"; a frustration. Or, you can look at this as a truly dynamic thing, and an opportunity to see and create an ever-changing environment in your aquarium.

As in Nature, you can let the leaves decompose completely, adding new ones as you see fit, or you can simply replace leaves the minute they don't meet your aesthetic standards, so you always have fresh-looking, pristine leaves in your aquascape. Some hobbyists do this and, I admit, are able to enjoy leaves as "set pieces" in their most pristine set on a more-or-less continuous basis in their aquariums.

It just seems like a hell of a lot of work to me!

And, being relatively inexpensive as compared to say, plants or driftwood, leaves are one of the more economical aquascaping "props" you can use, making these quick changes affordable!

When we sort of get over the whole "purely aesthetic" thing when it comes to leaves, and let yourself make the mental shift to understand that they are functional first, and that the aesthetics are a part of the function, it all starts making sense.

In Nature, as we've discussed many times-leaf litter zones comprise one of the richest and most diverse biotopes in the tropical aquatic ecosystem, yet until recently, they have seldom been replicated in the aquarium. I think this has been due, in large part- to the lack of continuous availability of products for the hobbyist to work with, and a lack of real understanding about what this biotope is all about- not to mention, the understanding of the practicality of creating one in the aquarium.

Long-held fears and concerns, such as overwhelming our systems with biological materials, and the overall "look" of decomposing leaves and botanicals in our tanks, have understandably led to this idea being relegated to "sideshow status" for many years. It's only been recently that we've started looking at them more objectively as ecological niches worth replicating in aquariums.

What makes leaves fall off the trees in the first place? Well, it's simple- er, rather complex...but I suppose it's simple, too. Essentially, the tree "commands" leaves to fall off the tree, by creating specialized cells which appear where the leaf stem of the leaves meet the branches. Known as "abscission" cells. for word junkies, they actually have the same Latin root as the word "scissors", which, of course, implies that these cells are designed to make a cut!

And, in the tropical species of trees, the leaf drop is really important to the surrounding environment. The nutrients are typically bound up in the leaves, so a regular release of leaves by the trees helps replenish the minerals and nutrients which are typically depleted from eons of leaching into the surrounding forests.

(And the rapid nutrient depletion, by the way, is why it's not healthy to burn tropical forests- the release of nutrients as a result of fire is so rapid, that the habitat cannot process it, and in essence, the nutrients are lost forever.)

Now, interestingly enough, most tropical forest trees are classified as "evergreens", and don't have a specific seasonal leaf drop like the "deciduous" trees than many of us are more familiar with do...Rather, they replace their leaves gradually throughout the year as the leaves age and subsequently fall off the trees.

The implication here?

There is a more-or-less continuous "supply" of leaves falling off into the jungles and waterways in these habitats, which is why you'll see leaves at varying stages of decomposition in tropical streams. It's also why leaf litter banks may be almost "permanent" structures within some of these bodies of water!

In the wild habitats, leaf litter beds function as a means to preserve the nutrients that would be lost to the forests which would inevitably occur if all the material which fell into the streams was simply washed downstream. The fishes, crustaceans, and insects that live in the leaf litter and feed on the fungi, detritus, and decomposing leaves themselves are very important to the overall habitat.

In the properly-constructed and managed botanical-method aquarium, I believe that leaf litter certainly performs a similar role in helping to sequester these materials, providing a means of nutrient processing, physical shelter, and supplemental food for the inhabitants of the aquarium. Ive said it before, and I'll say it again:

Decomposing leaves are the "fuel" which powers a botanical-method aquarium.

One interesting observation I’ve made over the years concerning adding leaves to the aquarium and letting them decompose completely: Dead, dried leaves such as those we favor don’t have nearly the impact on water quality, in terms of nitrate and phosphate, as "fresh" leaves do. I’ve routinely seen undetectable nitrate levels in aquariums loaded with botanicals. This is largely because dead, dried leaves have depleted the vast majority of stored sugars and other compounds which lead to the production of nitrogenous substances in the confines of the aquarium.

So, leaving leaves in to fully decompose likely reaches a point when the resulting detritus is essentially inert, consisting of the skeletonized sections of leaf tissue which can decay no further. Dead leaves contain largely inert forms of polysaccharides, and are rich in structures like lignin and cellulose- materials which seem to have little impact on the water quality in our tanks.

Oh, and performing regular water exchanges can’t hurt, either!

The whole idea of utilizing leaf litter in our tanks and embracing its function is an exciting field of study for our community! The benefits that we can realize are only now starting to be more thoroughly considered and understood by aquarium hobbyists.

Overcoming our ingrained aesthetic preferences, and accepting the function and appearance of decomposing leaves as a natural, ephemeral, and altogether unique habitat to cherish in the aquarium is a decision that each one of us has to make- but if you look at it from a "functional aesthetic" viewpoint, it’s pretty easy to appreciate the “beauty”, in my (very biased!) opinion!

Keep an open mind. Make appropriate mental shifts. Experiment freely and responsibly. Share your successes, failures, and everything in between with our fellow hobbyists.

So, I may or may not have made my case that leaves make lousy "hardscape" pieces for aesthetic-forward approaches, but I hope I've validated my opinion that they provide many incredible functional benefits for our aquariums.

Stay thoughtful. Stay creative. Stay observant. Stay bold. Stay diligent...

And Stay Wet.

Scott Fellman

Tannin Aquatics