What a cheerful, confidence-building title, huh?
Well, it's honest, at least!
I suppose one of the most commonly asked questions I get here is, "How many ________ does it take to tint my water?"
And my most common response?
"I have no idea!"
Pretty much NOT the response that you'd expect from someone who curates, obsesses over, and sells leaves for a living, I know. But here's the thing: There are a ton of variables, such as the composition of your water, the size of the aquarium, water movement, where you incorporate them in your system (i.e., in a filter chamber, canister, reactor, or the display itself), and wether or not you utilize some form of chemical filtration (such as activated carbon, etc.), and exactly WHAT your goal is for using them in your aquarium, just to name a few.
Leaves are really tricky little bastards, when it comes to "how many?"
I can tell you, as a sweeping generality, that it typically takes me at least 2-4 ounces of Texas Live Oak leaves, Yellow Mangrove Leaves, or a dozen or more Guava and Jackfruit Leaves to get a decent level of "tint" in an aquarium of say 30-50 U.S. gallons, when simply placed in the tank. Catappa leaves? Well, it typically takes about 10-12 medium-sized ones to do the job in my tank.
Guava, Jackfruit, and some other leaves tend to impart a less significant tint to the water in my experience- an almost yellowish-gold color, so you can use more of them, especially in conjunction with Catappa, to achieve a great affect!
And the pH thing?
Now, I"m starting with RO/DI water with essentially no carbonate hardness and a very "flexible" pH. Not only do the botanicals influence the color, but they can influence the pH under these circumstances. Simply adding catappa or other leaves to your hard, alkaline tap water will have little to no effect, other than to impart some color and maybe increase your TDS a bit.
However, the tannins, which are the substances which tint the water, cannot "overcome" the Calcium and Magnesium ions, and drive down the pH significantly in water with high levels of these carbonate hardness present. It simply is putting more materials into the water (which are often detectible by TDS meters in aquariums).
Remember, there are multiple factors in play, and multiple goals you might have for adding leaves to your tank. If it's just about the aesthetics of having leaves in the tank, and you want clear water, use activated carbon in your filter and call it a day! If you're all about a deeply tinted and low pH environment, you need to eliminate activated carbon in large quantities, employ RO/DI water, and likely use quite a bit more of these materials than I am talking about here.
You have to experiment. There is simply no "recipe" out there that can give you "Instant Amazon" conditions by adding "a little of this and a bit of that" to your tank, despite what "experts" or vendors will tell you. There just isn't. Period.
I could talk until "the cows come home" about how much of this and that I use in my tank- but I may have a combination of factors that are vastly different from the environment in your aquarium. Sure, you can get a general idea- but your results will vary. Every tank is different. I think it's more about understanding the general "practices" involved versus how many of whatever to add.
In my display tank in my home, I use a rlot of Yellow Mangrove and Texas Live Oak, with a bunch of Borneo Catappa Bark and Oak twigs to achieve a nice color that I like. I also have a pH of around 6.6 and undetectable carbonate hardness; a TDS of around 10 (interesting....). Oh, and I use a hardscape comprised of "Spider Wood", which, especially when "fresh", imparts hella tint to your water! I'd almost call the use of wood a "hack" when it comes to visual tinting of water...
But that's me.
Back to the subject of chemical filtration in blackwater tanks for a bit...
Now, I've already touched on the issue of chemical filtration and its impact on removing the tint and tannins associated with leaves and botanicals. It's entirely possible to minimize or render the ph-lowering and water-tinting capability of tannins released by leaves with activated carbon, Purigen, or other chemical filtration media. Tannins are rather weak acids, yet they can lower the pH of water when their is less "buffer" in the system (i.e.; lower general hardness). Just how much tannins can lower pH in a given system depends upon how much buffering capacity the water has.
With "harder" water (i.e., water with a greater buffering capacity), you can have the tinted water look from leaves and wood, without the pH reducing effects, particularly if the tannic acids are absorbed by the aforementioned chemical filtration media. So, in other words, you can have the aesthetics of blackwater while running your aquarium at a higher pH if the hardness is sufficient. Once you remove tannins in a lower hardness system, your pH should rise, too, since you're removing the acids.
Woah. Head spin time.
Bottom line is this: You can use chemical filtration media in "tinted" tanks. However, depending upon the amount of media, quantity of tannin-producing items (leaves, wood, botanicals, etc.) and the capacity of the aquarium, the impact will be variable. I run chemical filtration media (Purigen and activated carbon) in my tanks, and I still have nice tint and pH relatively stable, as mentioned above. It's a fine line between "too much" and "too little", and you will simply have to experiment to find what works best for you!
And more water chem talk?
Again, I attribute my relatively stable soft, mildly acidic conditions to the use of reverse osmosis/deionization (RO/DI) to pre-treat my tap water. RO/DI units are a bit pricy at first, but IMHO, they are an essential piece of a equipment and a very wise investment for the aspiring BWBS hobbyist!
Remember- Botanicals and leaves will NOT soften your water. It's perhaps the most misunderstood thing of all about botanicals? Maybe. I think it's easy to see how this one got started and tends to hang around a bit. Most botanical materials contain tannins and humic substances, which can drive down the pH in water with little to no carbonate hardness. And of course, the tinted, soft acidic water in many natural habitats often has an abundance of leaves and botanicals present. I think that this gave a lot of hobbyists the impression that you could simply add some of these materials (leaves, etc.) into your tap water and create "Rio Negro-like" conditions easily!
This can only be accomplished with reverse osmosis or ion exchange( a process in which calcium and magnesium ions are "exchanged" for sodium or potassium ions.)
Reverse osmosis is a water treatment process which relies on a membrane which has pores large enough to admit water molecules, yet "hardness ions" such as Ca2+ and Mg2+ remain behind and are flushed away by excess water. The resulting product water is thus called "soft water"-free of hardness ions without any other ions being added.
Get an RO/DI unto and be done with it...
And it is now widely accepted by science that humic substances (such as those present in botanicals) are thought to have a wide range of health benefits for fishes in all types of habitats. We've covered this before in a great guest blog by Vince Dollar, and the implications for the hobby and industry are profound. Although they are not the "cure all" that many vendors have touted them as, leaves and other botanicals do possess a wide range of substances which can have significantly beneficial impact on fish health.
How often do you need to replace your leaves and botanicals Well, another great question for which there is no "rule" involved. The reality is that you can simply add new leaves on a regular basis, so you'll always be making up for the ones that have decomposed. Some hobbyists like to remove the decomposed leaves, preferring a more "pristine" look.
It boils down to aesthetics, really.
This tinted world we play in, with its cool aesthetics, confounding chemistry, and abundance of assumptions and "aquarium hobby urban myths" is really something, isn't it? You just read almost 2,000 words telling you that there is no single way to achieve your goal...not exactly earth-shattering, but entirely symbolic of this fascinating world were in!
Be bold and experiment...find your path to tinted Nirvana!
Stay curious. Stay diligent. Stay engaged. Stay skeptical. Stay excited. Stay open-minded...
And Stay Wet.