When it comes to techniques and such, the best part about the natural-style, botanical influenced aquariums that we love so much is that everything is still evolving. I mean, sure, we build upon work that hobbyists have been doing for decades; however, the application of existing technique to our approach is ripe for refinement and evolution.
One of the more "basic" requirements of any aquarium is filtration. And with filtration, you have the collateral effect of water movement in the aquarium. This is a topic to which we as aquarists typically give modest amounts of thought, other than determining what type/size of filter to use in our tank. Then, it's on to sexier topics, like "Which piece of Manzanita do I use...?"
The reality is that, in a botanical-style natural aquarium, filtration and water movement are influential and pretty important in the grand scheme of things. As with any aquarium, it's important to apply filtration that keeps up with the specific needs of your tank and its inhabitants. Of course, with the heavily botanical-influenced aquarium, there is the added consideration of all of those leaves and pods and such.
These items not only are part of the "hardscape"- their ephemeral nature makes them a component of the bioload of the system- and due consideration needs to be paid to their impact on the closed system's environment. Remember, leaves, seed pods, and the like are "ephemeral"in many respects, slowly decomposing and breaking down, releasing not only "bits and pieces", but organic materials as well.
That's where filtration comes in.
Now, Nature provides "filtration" in the form of the nitrogen cycle and the bacteria which accompany it. Bacterial biofilms- the bane of many a new aquarist- are actually a true benefit because of what they are comprised of (bacteria, hello!), and for the potential supplemental food source they become...Oh, I"m digressing, yes. And of course, fungal growth on the botanicals also serves to physically break down and "process" some of the botanical materials and their accompanying organics.
Of course, as fish geeks, we aren't just going to rely on bacteria and fungi to do the "heavy lifting" of filtration for our tanks...Nope, we need some help. That's where filters come in. The first consideration is, of course, choosing a filter system of the appropriate size for the tank you're working with. That is kind of a "no brainer", since we typically all know how to do that (ahhh, I'm assuming)- and if we don't, we can easily research this topic on hundreds of sites all over the 'net.
My two cents on the topic? I'd choose the largest/most capable filter your tank can reasonably accommodate. That's the reefer in me talking, but that's my take. Better to have more than you need than not enough...Notice I didn't say "too much?" Because you can never have "too much" filtration capacity, IMHO. 🤓
So, what kind of filter is best for a natural-style "botanical-centric" aquarium? Personally, I like using "all-in-one" tanks with built-in overflows and filter compartments- but that's me- and we an chat about that some other time. The bulk of enthusiasts I work with would tell me that they favor canister filters like Eheim and the like. And it's hard to argue with that choice. They provide high capacity, the option to utilize multiple filter media (ie; mechanical, chemical, biological), are easy to service, relatively unobtrusive- and for the most part, highly reliable.
I like filter systems that give you the option to utilize different types of filter media, so although I love air-driven sponge filters- and they work fine- they're not my top choice. And of course, hang-on-the-back outside power filters and some internal filters give you the same flexibility. It really boils down to economics, aesthetic preferences, and your ability to maintain the filter.
Keep in mind that, if you like the look and benefits of botanicals (ie; tinted water, humic substances, etc) but don't want to see leaves and crumbling, biofilm-encrusted seed pods in your tank, then the canister and outside power filters give you the option to run these materials as "media", and you can have your display tank as "botanical-debris-free" as you want, while still getting that tinted look.
Yes, media-holding filters give you options.
Now, with regard to flow or water movement within the aquarium itself, there are multiple schools of thought, of course. I'll give you my "two cents worth" as a botanical style natural aquarium geek.
So, here's the deal- many of the blackwater habitats that we obsess over have minimal to virtually non-existent water movement. You know, slow-flowing tributaries off of main streams, flooded forest floors, vernal pools, etc. And those are certainly something you can and should replicate in the aquarium. However, in my opinion, the flow that we create in the closed system aquarium is not only typically less than the velocities found even in relatively mild natural conditions- it serves the added purpose of keeping oxygenation up and preventing stratification of pH in the tank.
I mean, sure- stagnant is stagnant, right? However, most of us are not trying to create a stinking, stagnant, "malaria swamp" habitat- so some water movement is desired. Of course, Betta and killie keepers have reasons for minimal current/surface agitation's I get that it's not a hard and fast rule in every circumstance. However, for most hobbyists- and fishes- some current/water movement in the aquarium is desired.
In a tank featuring botanicals, water movement (I've been going back and forth using the term "current" as well- which I know is confusing...Let's just call it "water movement" from now on to avoid confusion) is desired. However, you want to avoid directing filter outputs right into your leaf litter bed, for example. Otherwise, you end up with leaf litter in various states annoyingly flopping around and traveling about the aquarium. That's really annoying.
And it's also disruptive.
Remember, in many natural habitats in which leaves are present, the water movement into the litter bed is relatively modest. It might be greater over the litter, but it's relatively modest in the litter itself- perhaps even virtually undetectable. This affects fish population. In fact, a study on floating leaf litter beds I stumbled upon highlighted this little gem:
"Several species show adaptations for living under low oxygen conditions, which possibly allow them to occupy confined spaces inside the banks. On the other hand, several species were observed at the periphery of the floating litter banks and may benefit from the stronger currents and higher oxygen levels that result from the positioning of the floating litter banks at the water's surface."
And of course, as fish geeks, we want to encourage healthy environmental conditions in our tanks- and to keep our fishes happy and active for long lives- so water movement and oxygenation in the overall aquarium environment is vital. In practice, I direct modest current into the tank above the litter bed. Inevitably, because of the geometry of our tanks, you'll see leaves moving about just a bit, and that's okay. Some movement in the botanical bed in an aquarium is good- it keeps excesses of fish waste or biofilms from accumulating in one specific location, assuring greater overall system stability.
So- the long and the short when it comes to water movement- it's a good thing I the botanical-style aquarium, as long as you're not blowing everything all over the place!
In the aquarium, filtration and water movement tend to go hand in hand. This is intended only as the most brie intro to the topic to "lay down a marker" for us to discuss as a community on social media on an ongoing basis. There are numerous opinions and ideas and thoughts out there on this topic- I hope this serves as a "fire starter" to ignite further discourse!
I the mean time, keep your filter on. Keep your tank water moving. Keep your eyes on your fishes...
Stay engaged. Stay interested. Stay diligent...
And Stay Wet.