I admit it freely: I'm a sucker for tinted water, decomposing leaves, seed pods, and an aquatic aesthetic which would likely have the most hardcore "Nature Aquarium" fan running for the carbon.
Of course, there are a lot of different things we can do with botanical materials besides just "tint" the water. It's important to realize that materials like seed pods, leaves, bark, etc. are found in a variety of aquatic habitats all over the world, and their influence is more than just that pretty look. And, even with their presence in most every wild aquatic habitat of the world, they don't always result in brown water.
And, yes- it is absolutely possible (and entirely realistic) to have an aquarium filled with botanical materials that does not have the lovely "cafe au lait" look that we all know and love so well! In a twist on one of our own marketing slogans, "It's okay NOT to tint..."
Although the three "classical water types" (white, black and clear) are used by science to describe many of aquatic habitats, we aquarists tend to classify water as "blackwater" or "clearwater", which, although not scientifically "pure", and likely earns us the coveted "WTF" from scientists, tends to make our understanding and discussions easier!
It's certainly not a given that the presence of leaves, wood, and other botanical materials in a given body of water will result in brown water and low pH. Rivers like the Juruá, Japurá, Purus, and Madeira) are turbid, with water transparency that varies, and they transport large amounts of nutrient-rich sediments from The Andes. Their waters have near- neutral pH and relatively high concentrations of dissolved solids.
I have no illusions about almost any aquarist deliberately wanting to recreate "turbid" water conditions in his/her tank- blackwater or otherwise-so I suppose we an eliminate that as a candidate for replication by all but the most "hardcore" of the hardcore hobbyists.
The Rio Xingu and Tapajós, on the other hand, are classic examples of "clearwater" rivers. One of the largest tributaries of the Amazon, the "Xingu" has an abundance of rock, and a higher content of dissolved minerals than a blackwater habitat like the Rio Negro. There is not much suspended matter because the rock formations which the river courses through are ancient and no longer erode in the current. The pH varies between 6 and 7.
And the fishes you'd keep in a Tapajos-themed (notice I didn't say "biotope", because that's a different level of detail, of course!) are legion. It's estimated to be home to at least 500 fish species! Favorites like the aforementioned Dwarf Regani Pike Cichlid, Festivum, Geophagus, Checkerboard Cichlids (D. maculatus), Pristella Tetra, Pencilfishes, Leporinus, a bunch of Hemigrammus species, and even some Apistos are just a few of the many aquarium species at home in this type of habitat. This makes replicating this habitat a perfect challenge for the geeky aquarist!
As we've mentioned many times, water color, although helpful to us aquarists in some respects, is not a reliable indicator of the pH or ionic composition of the water! There is no substitute for good, old-fashioned water testing!
Interestingly (and perhaps, confusingly) the lower section of some Amazonian black-water rivers such as the Rio Negro, Tefé, Uatumã and Urubu in Brazil; Nanay in Peru and some streams in Colombia can have ionic composition and/or pH-values similar to the white water rivers, and not like the typical Amazonian blackwater rivers. It is thought by researchers that low electrical conductivity values can be responsible for this phenomenon.
Now, sure, we could go on and on and on talking about all sorts of different wild aquatic habitats and how botanical materials influence both the water chemistry and the appearance of the water and habitat. There are countless "variations on a theme" here that have implications for keeping a huge variety of tropical fishes.
The implications of all of this stuff are that, if you're looking to accurately recreate the water conditions from which the specific fishes you keep come from, you would be well-served to determine, as accurately as possible, where they originated from. With wild-collected stock this might be easier (assuming the collectors/distributors possess and make this information known (Hear that guys? A good idea!) to hobbyists, the ultimate "end users" of their "product' (that sounds awful, calling fishes "product", but I think you get the point...)
This brief, highly-generalized discussion was not intended to be the last word on this topic. Merely a brief introduction of some "talking points" that we as hobbyists can use for further research and discussion for this interesting and most important topic.
Now, there are numerous approaches to preparing water for our aquariums, and many, many different viewpoints and ideas among hobbyists as the "best" way to do things. However, at the end of the day, we all need to operate in a manner which we can understand, consistently replicate, and are comfortable with. And so much of this comes with education, discussion, and sharing of ideas.
Study. Experience. Create. Contemplate. Report.
Stay bold. Stay open-minded. Stay excited. Stay intrigued. Stay creative...
And Stay Wet.