Apart from, "What are your favorite botanicals?", the question we receive the most here at Tannin Aquatics is, "How many do I need for my ___ gallon aquarium?"
And you'll just love my answer: I don't know.
Seriously. It depends. And I'm not trying to be evasive or noncommittal here. The reality is, it depends on a lot of factors, not the least of which is your aesthetic. Let's examine each of the main factors that will influence your decision about how many botanicals to add to your aquarium.
First off, there is no "secret formula" that we have developed to tell you exactly how many of which botanical will produce a given amount of "tint" in the water. It's virtually impossible to do this, because the degree to which the botanicals influence your water's tint is influenced by a myriad of factors, including the pH, amount of flow, what types (and how much) of chemical filtration media you employ (if any), the size of the aquarium, where you place the botanicals (i.e.; in a filter or reactor, or just on the substrate), etc.
It really boils down to a few things (in no particular order):
What type of look are you trying to achieve? It goes without saying that if you are trying to replicate an Orinoco Basin "blackwater" tributary, with it's accompanying lower pH and tint, then you'd probably want to either go heavier on the botanicals (i.e., volume of botanicals to water volume), or employ botanicals which have shown to inflect water coloration and chemistry more significantly. For example, you'd be advised to use greater quantities of Catappa leaves, Catappa bark, Coco Curls, "Fundo Tropical", "Encontro Pods", Alder Cones, Casuarina Cones, Banana Stem pieces, etc.
Do you want the botanicals to be the main aesthetic feature, or just a compliment? Yup, we've seen a number of aquariums recently where the goal was to utilize the aquatic botanicals (particularly the larger, more "permanent" ones, such as "Jungle Pods", "Savu Pods", "Tapete", "Ra Cama", etc.) as the major part of the hardscape. And, in smaller aquariums, the concentration of these botanicals can definitely influence the water chemistry and appearance.
At this point in the discussion, I should point out that it is absolutely possible to utilize aquatic botanicals in your aquarium- even in significant numbers- and not let them tint the water. By utilizing chemical filtration media, such as activated carbon, Purigen, Poly Filter, or a combination of them, you can enjoy the aesthetics of aquatic botanicals without any tint. I know this for a fact, of course, because I've done this myself as part of testing. Also, some of the beautiful aquariums from Aquarium Design Group that we've featured on our site and in our social media, which employ significant amounts of botanicals, are typically devoid of tint by using the aforementioned filter media.
Do you want to utilize the botanicals to influence water chemistry? If you do, we highly suggest that you not only use generous amounts of Catappa leaves and/or Alder Cones (for which there have been some rough guidelines worked out over the years as to how many you'd want to start with in a given water volume), but you'd probably minimize the use of chemical absorption media, like activated carbon, as these will typically remove some of the tannins and humid acids which you're trying to put to work in your aquarium. We also suggest that you throw in a few Catappa leaves or Alder Cones in your source water storage containers, so that they can leach the desired substances into your water that you'll use for water changes and top off, thus maintaining a more stable environment for your aquarium.
There is no substitute for proper preparation of your botanicals before using them in your aquarium. This is a vital step in the process, and can help avoid many potential problems. Look, we're talking about adding dried plant materials of terrestrial origin to water. They are going to react. They will release substances that will influence water chemistry and coloration, but you can control the degree to which they do so through some of the aforementioned methods. Also, longer "post boil soak" periods can help leach out some of the initial burst of tannins released from these materials with the passage of time.
You will see the famous (or is that, "infamous"?) "Biofilm Phase" in many cases, where your beautiful selection of botanicals is covered by a layer of bacterial "sung" and "fungus." We strongly advise you to "wait it out" when this happens, and simply scrub the botanicals with a medium-bristle toothbrush if you can't handle looking at it, as well as employing animals such as ornamental shrimp, catfish, etc. to give you a "biological assist" during the "maturing process."
I equate this "Biofilm Phase" with the "cycling" of a typical freshwater or marine aquarium. You may not experience a buildup of this "gunk", but odds are that you will. It's simply a "right of passage" for anyone playing the "New Botanical" style aquarium game. We receive periodic emails and calls from concerned aquarists (and rightfully so), who get a bit freaked out seeing their displays covered in this yucky stuff after the initial "honeymoon period", and I'll tell you what I tell them: It's normal. It's never been responsible for a single fish death that I've seen. It will go away.
The degree of "intervention" (i.e.; how much scrubbing, swishing, and/or re-boiling) you might want to engage in is entirely dependent upon your tolerance! It can be several weeks, so it's something everyone needs to think about. And, if you're lucky, you might not even experience this. It's no different than what you see when you first submerge many of the types of driftwoods that we use in aquariums, so no real cause for panic. Occasionally, a pod might have a nasty, "rotten egg" smell, in which case we do suggest removing it and either re-boiling it or discarding it. I might add that this is uncommon, and not particularly dangerous unless you have a small water volume and a lot of fouling botanicals, or have already shaky parameters in your aquarium.
Algae is another consideration. Yup, like any "undefended" substrate in the aquarium (i.e.; wood, rock, hardware), botanicals will "recruit" some algae- the degree to which is entirely dependent upon your water parameters- and your tolerance for such things. We are rather fond of some algae in our systems, as it creates an entirely natural look, and is beneficial for many fishes, particularly those which like to "graze" in nature, so I don't go to any great lengths to eradicate every single patch as soon as I find it. You might be different, so knock yourself out!
Finally, regardless of how you employ the botanicals, I cannot stress enough the need to go SLOWLY. There is no need to rush and dump everything in at one time, or in huge quantities. Particularly in an established aquarium, where your animals are used to a certain stable range of parameters...It goes without saying that if your introducing materials which can influence water chemistry and quality, you will need to go slow and exercise common sense. And, since botanicals are actively "breaking down" in your aquarium over their "service lifetimes", it's important to employ good husbandry techniques (i.e.; monitoring of water quality, water changes, regular filter media changes, etc.). Just remind yourself that aquatic botanicals create a "dynamic" environment, and you'll enjoy using them that much more!
So, there is another quick run down on the aesthetic, environmental, and practical considerations of using aquatic botanicals in your aquarium. I probably created almost as many questions as answers, but I'd like to think that we opened up your eyes to the possibilities of using these amazing natural items in your aquariums to create fascinating, ecologically diverse displays.
Stay fascinated. Stay enthusiastic.