I admit, I am not the go-to authority on anything about aquatic plants.
In fact, you'll be best served by asking anyone- like, your non-aquarist neighbor, the dog groomer, or even the barista at your local coffee house- questions on aquatic plants before you think of asking me for advice on them! This should hardly come as a surprise to those of you who know me personally! I'm not known for lush, pristine-looking, meticulously-planted aquariums!
I have kept plants many times over the years. My current home "Asian-themed" blackwater aquarium actually has aquatic plants in it- but they fail to ignite my passion for some reason. Yet, I don't know a Riccardia from a Riccia. And it doesn't really bother me. I appreciate aquatic plants. I enjoy looking at planted tanks...They just don't make my heart skip a beat with excitement. "Estimative Index", "Dry Start", "Walstad Method?"
Might as well be speaking another language.
Yeah, that's my "jam" on aquatic plants.
That being said, there is one "plant"- well, a tree, actually that grows in aquatic environments, which I have become obsessed with over the years...The Mangrove.
Specifically, the "Red Mangrove", Rhizophora mangle. The one we'll focus on here and refer to as "Mangrove" for the purpose of this piece.
Hardly what you'd call an "aquarium plant"- I mean it's a tree.
That being said, the Mangrove is an amazing tree that certainly has applications for aquariums- specifically, brackish aquariums. Now, without going into a long, long, recap of what mangroves are and how they function (You can Google this stuff and get hundreds of hits with more information than you could ever want), let's just say that mangroves are a group of trees and shrubs which live in the coastal intertidal zone, in areas of warm, muddy, and salty conditions that would simply kill most plants.
They possess specialized organs which allow them to filter out sodium, absorb atmospheric air through their bark, and generally dominate their habitats because of these and other remarkable adaptations.
There are about 100-plus different species, all of which are found between tropical and subtropical latitudes near the equator, as they are intolerant of cold temperatures. Mangroves put down extensive "prop roots" into the mud and silt in which they grow, giving them the appearance of "walking on water." These root tangles help them withstand the daily rising/falling tides, and slow the movement of the water, allowing sediments to settle out and build up the bottom contours of the local ecosystem.
And of course, the intricate root system not only protects coastlines from erosion, it plays host to a huge variety of organisms, from fungi to bacteria to crustaceans to fishes. The fishes use mangrove habitats as a feeding ground, nursery area, and a place to shelter from predators.
Okay, you get it. But how do we use these trees in the aquarium. And wait a minute, you're talking about a tree? WTF?
Well, yes. I am. No, fist off, before you part going off on me about their unsuitability for aquariums or some ethical implications for their "removal" from the wild, let's talk for a second about how we acquire them and how they grow. First off, removing a growing mangrove tree or seedling from the natural environment is unethical, illegal in most areas, and essentially idiotic.
NO one should even consider doing that. Period.
Rather, we acquire mangroves as propagules- buoyant seedlings which grow through the fruit, and can produce its own food through photosynthesis. When the propagules are mature, they fall into the water, and can remain in a dormant state, withstanding desiccation, for more than a year! Propagules are buoyant and can float until they find suitable "anchorage." When it's ready to take root, a propagule will change its internal density to float vertically, rather than horizontally, to make it more likely to root in suitable sediment.
As aquarium people, we start with these free-floating propagules, which are abundant and legal to collect in places like Florida, where the adult plants are protected from harvest or pruning. The advantage of propagules is that they can be stored in a moist environment and easily shipped in damp paper towel, and stored that way for extended periods.
So, once you have one of these pickle-like propagules, how do you use it?
First off, you don't need to "root" it, or "plant" it in substrate. You simply need to anchor it in the water column in a vertical position, and allow it to extend roots down towards the bottom on its own pace. I have typically done this in relatively small containers of water, like a jar, vase, or pitcher, before translating it to the aquarium.
You'll know that the propagule is ready to transplant when it becomes a "seedling"- with little roots showing up on the bottom, and leaves beginning to unfurl on the top of the propagule. You can sprout the propagules in all sorts of light conditions- typically even room ambient lighting (as in a windowsill) will do the trick.
Fluorescent, LED, or other aquarium-rated "daylight" lighting will accomplish this, too. Of course, the part with the leaves needs be anchored above the water line (yeah, people ask me this question regularly). Like everything we do in the "natural-style" aquarium game, patience, diligence, and observation are essential when keeping Mangroves.
If using an artificial light source, be sure to mount the light well above the container or aquarium where the mangroves are kept. This not only results in a more natural-looking growth form- it keeps the leaves from growing literally right into the light and frying themselves (I've done that many times, lol).
Once they are placed in the aquarium, you should anchor them near the water surface, not in the substrate. As discussed many times before, I've chosen to attach my propagules to (legally-collected) mangrove root pieces in my brackish- water aquarium, and that works really well.
Allow the roots to "find' the bottom for themselves. This will encourage the growth of a strong, almost "woody" prop root system that these trees are famous for. It may take many months for them to achieve "touchdown and penetration" into the substrate, but they will- and a stronger plant ensues as a result of allowing them to do it themselves!
One little word of advice: Be sure to sprout your mangrove propagule in the same water conditions (ie; marine, brackish, fresh) as you will be keeping them in perpetuity in your aquarium. They categorically don't adapt well to habitat changes once they have begun to grow.
Now, what kinds of substrates should you use? Well, keep in mind they come from muddy, sedimented, nutrient-rich environments in Nature, so they can handle just about anything. I've personally utilized everything from marine biosediments to aragonitic sand, to mixes of pond soil or aquatic plant soils. You can mix in peat and all sort of substrate enhancement materials to provide sustenance and proper rooting for these hardy trees. A little online research can yield lots of great tips on substrate mixes for mangroves in the captive environment.
The beauty of mangroves is that they're pretty hardy- which bodes well for their care in the aquarium! You need to do little more than illuminate them, anchor them in a vertical position above substrate, and mist the leaves on a regular basis. This process helps to keep dust, salt build-up (which is exported via the leaves), and insects off of the leaf tissues.
Now, again, we'll often hear arguments that keeping a tree in an aquarium is kind of crazy. I admit, a full-grown mangrove tree is virtually impossible to keep in a home aquarium. However, these trees grow incredibly slowly, reaching "houseplant-like" sizes after a year or more in captivity. And, with frequent pruning, you'll see that they can be maintained in almost a "bonsai-like" size indefinitely- all the while putting down the extensive, intricate root systems that they are so famous for.
One of the cool benefits of mangroves in the aquarium- much as in Nature- is that their roots will recruit and foster the growth of microorganisms, fungi, algae, and other epiphytic life forms, providing a foraging place for fishes, and the ability to contribute to the biodiversity and healthy function of your aquarium ecology.
In addition, the "leaf drop" which mangroves are known for accomplishes the same thing it does in Nature: Helping to provide leaf litter, which encourages the growth of microorganisms and other life forms, and tinting the water via exudation fo tannins and humic substances. As you might guess, I encourage the fallen leaves to accumulate and decompose in the aquarium!
Notice I don't talk about utilizing mangroves as a "nutrient export" mechanism in your aquarium? This is because it would take many mangroves (like, more than your tank caudal accommodate) over many years to provide any noticeable nutrient export effect on your tank. Rather, we choose to focus on their unique aesthetics and their ability to foster the growth of other, beneficial life forms.
Sure, we could probably go on and on about keeping mangroves in your aquarium (and probably will again I the future), but I hope that this admittedly superficial "quick start" guide will encourage you to research more about these remarkable trees and try them in your aquarium.
If you're fascinated by these amazing, adaptable trees, can obtain them legally and responsibly, and are up for the challenge of keeping them over the long haul, mangroves are a fascinating and attractive addition to your specialized natural aquarium!
Until next time...
Stay curious. Stay patient. Stay resourceful. Stay diligent...
And Stay Wet.