The thought: Many of the habitats we wish to replicate are very shallow in depth, relative to their width. Something we should consider in our aquarium design and execution?
I don't know about you, but for about the last maybe 15 years, my preference in aquariums has always led me to the "shallow, wide" footprint. This was very popular in reef keeping, as it put minimum distance between light source and corals. And I've noticed that this footprint is more and more popular with freshwater planted aquarists, too.
My last custom acrylic aquarium had dimensions of 40"x40"x22" (101.6cm x101.6cm x 55.88cm), 152 US gallons (575.38L)- and it created an amazing seagrass biotope tank. I had it re-finished, refreshed, and modified a bit, and it's going to become my ultimate Igarape tank in the near future!
I'm thinking even shallower (is that a word?) tanks are a cool idea for botanical-style blackwater aquariums (and for brackish tanks, too!), because they are proportioned correctly to mimic the relative water depth of the unique inundated Igapo forests or African vernal pools and Asian streams that hold a lot of fascination for us! If you do a little research, it turns out that many of these bodies of water a stunningly shallow, and this has interesting implications from both a functional and an aesthetic standpoint. And there are a number of commercially-made "production" tanks in these types of dimensions.
An interesting study of just one Igapo area in the Amazon revealed interesting "stats" in regards to depth of water and leaf litter.
In an area where the water depth was a maximum of 2 meters, the leaf litter depth was only about 20cm. In a very shallow side tributary, the litter depth was 10cm (about 4 inches), with the water level above it only 30cm (about 12 inches)! Now, these are just a few of many different areas affected by seasonal inundation, and there are areas that are several meters deep during peak months. However, on the average, many of the little Igarape that I found information on were at best a meter or two deep, with correspondingly deep leaf litter beds.
Obviously, most of us aren't going to use an aquarium that is much more than a meter in depth, but we can always utilize the ratio of water to leaf litter/substrate and play with whatever dimensions excite us. Nonetheless, I'm a big fan of shallow/wide, because if you do build up a nice botanical/leaf litter layer, you don't have a huge column of water above, and can really focus on some of the bottom-dwelling fishes which make these areas home.
I think an ideal tank dimension for a leaf-litter biotope-style aquarium would be something like 48"x 18"x 16" /121.92cm x 45.72cm x 40.64cm (about 60 gallons/227.12 L)...shallow and wide, indeed! With these kinds of dimensions, you could create a leaf litter bed over a thin covering of fine, white sand, with a depth of about (4 inches/10cm) and a water column of about 12 inches/30cm above it. This is a very good simulation of this type of habitat.
With a relatively low profile tank, you're not likely to feature Angelfishes in this tank! Rather, you'd focus on fishes like characins, including the leaf-litter dwelling "Darter Characins like Aphyocharax, Elachocarax, Crenuchus, and Poecilocharax. For interest, you could introduce some biotipically appropriate Hoplias and Otocinculus catfishes, too. For the "upper" water columns, you could play with specimens of various Hatchetfishes and Pyrrhulina, killies like Rivulus, and cichlids, such as specimens of Apistogramma, Aequidens, and Crencichla.
Obviously, this is just a guide based on some studies of these areas, and you can create your own species mixes and even specialize in one or two featured species found in these habitats (that would be VERY cool!). The important thing, in my opinion, would be that you are attempting to create a few different aspects of these unique habitats. Filtration could be provided by either a canister filter or an outside power filter, with flow directed towards the surface. Water temperature, based on studies, would be perfect if you could keep it at about 26 degrees C/78 degrees F. Now, the pH of many of these habitats that were surveyed averaged around 3.5-4.2- extremely acidic water with no real ionic content, that, as we've discussed previously, is something that is challenging to achieve, and equally as interesting to maintain (notice I said "interesting", because it's not impossible...just challenging). Thusly, a modest-sized aquarium operated at low pH would be a great "testbed" for various types of research into the maintenance of these types of biotopes.
We''ve noted from field studies that the primary decomposers in these low pH leaf-litter-habitats are fungi, and different types of bacteria. Fungi are most fascinating, because we see their "work" in botanical aquariums often. Those "yucky biofilms" many of us observe and bitch about on our leaves and botanicals are also visible fungi colonies...so we have some experience with them.
A shallow aquarium such as the one we're discussing would be perfect for observing and feeding challenging fishes, like the "Darter Characins", because they tend to be more difficult to acclimate to prepared or frozen foods. Feeding small quantities of living foods in a shallow aquarium would create ample opportunities for "target feeding" experiments with them!
Another advantage of a shallow, wide aquarium is a large surface area relative to the tank capacity, which can facilitate great gas exchange- something pretty important if a third of the tank capacity consists of decomposing leaves and botanicals!
Now, you don't have to build a custom-dimension aquarium. You can always simply partially fill a taller tank to achieve the ratio of water-to-substrate that we're talking about. I suppose one could argue that a deeper aquarium, filled well below its capacity, could more safely accommodate fishes that tend to jump, like RIvulus and Hatchetfishes!
Shallow and wide...good dimensions to play with, IMHO.
Sooo...this is just another one of those "botanical brainstorming" sessions...a little bit of context provided from nature, along with some thoughts about how/why we could incorporate some of these ideas into our aquariums...Let's see who's up for this! I'd love to see some of the stuff you are working on in this area! So many things to learn and discover...it's all very exciting!
As always, feel free to share pics, ideas, and successes...and failures, too. We learn from all of them!
Stay innovative. Stay focused. Stay excited.
And Stay Wet.