We receive a lot of questions about the long-term utilization of botanicals, and how they react and "function" in our aquariums. Specifically, we receive a surprising number of inquiries from hobbyists who either want a "darker tint" or want to know how to keep it longer.
So, first off, I need to be clear about one thing: I have no real scientific basis to back up my recommended ways of creating "darker" tint in your aquarium. I can make some recommendations of materials and ideas to do the job based solely on my experience and the experience of others who work with our botanicals.
Sure, you could achieve a darker, deeper "tint" in your aquarium by starting with materials which seem to have a different "tint capability", ie; botanicals which seem to impart more color into the water. My top choices for botanicals to accomplish that would be materials like Catappa bark (we offer three different types!), Red Mangrove bark, Alder cones, Red Mangrove leaves, Catappa leaves, Nypa Palm pods, Coco Palm bracts, Texas Live Oak leaves, oak twigs, and Banana stem pieces.
Although not an exhaustive list, these are some of the materials which have reliably and consistently produced darker "tint" in many of my personal aquariums and those of our customers. The bark and cones are, in my opinion, among the best of the best at releasing tannins for creating that nice dark color which so many of us love. If I had to select ONE item to do the most consistent job at imparting dark color, it would have to be Red Mangrove bark. This stuff can really color up water in a very short period of time!
Now, remember a couple of things: First, the color or intensity of the color is NOT an indication of the pH of the water! It's merely an indication that tannins are being imparted into the water. The extent to which they will do so is likely dictated by things as diverse and seemingly unrelated as the starting pH/carbonate hardness of the water, temperature, etc.
Oh, and botanicals will likely have limited impact on pH and NO impact on hardness of the water at all. If you're using reverse osmosis for water pretreatment, which yields pure water essentially devoid of carbonate hardness, the pH is much more easily and significantly impacted by botanical materials.
And of course, if you utilize many chemical filtration media- such as activated carbon or materials such as Seachem Purigen- to any significant extent, you're almost certainly removing a good percentage of the coloration as fast as the materials are imparting it into the water. These media excel at removing the tint and color which botanical materials impart into the water.
Sure, you can use these materials for their ability to remove dissolved organics or impurities and still keep some coloration (I do)- but you'd want to use significantly less than the manufacturer's recommended "dosage" in your tank. So, my first question when people ask me, "Why is my tank not staying tinted?" is, "Are you using chemical filtration media in your aquarium? How much?"
Other hypotheses which I have come up with about why some tanks don't achieve or maintain a significant tint is that we are often simply not using enough of the botanicals required to do the job. Notice that we offer very little in the way of "dosage" instructions about how much or how many botanicals to use in your aquarium. There are simply too many variables- some of which we brought up above- to make any kind of reasonably accurate or responsible recommendation. Rather, it's more about selecting the materials you like and adding them until the desired coloration is achieved and maintained.
The other thought I have (and this is where my weak understanding of chemistry is on glaring display) is that tannins (of which there are many)might have some sort of "half life", in terms of their ability to produce colors. And there might one some validity to this supposition. Think about wine, in which the coloration or taste imparted by tannins can degrade over time.
Well, just a thought, anyways!
And this thought brings to mind a concept that we have embraced as long as we've used botanical materials in our aquariums:
Botanicals are ephemeral- they decompose steadily, at a speed dictated by their environment, their physical size, how much tannin is contained in the tissues of a given seed pod or leaf, and chemical and physical composition of your water- among other factors- and in order to maintain consistent conditions/coloration, we advise continuous replacement of these materials as they break down. Particularly in situations where you're doing a lot of water exchanges, or utilizing significant amounts of the aforementioned chemical filtration media. Consider botanicals as "consumable" items, requiring regular and consistent replacement in the aquarium.
And of course, drawing our inspiration from Nature- this makes sense...In natural aquatic habitats in which leaves, seed pods, and other botanical materials are present, there is typically a continuous "replenishment" of them. As some materials completely decompose, new materials are continuously falling from the trees or being washed into the water via external forces (ie; weather, seasonal leaf drop, etc.). This continuous parade of materials into the aquatic system helps maintain a stable, consistent environment.
Oh, and a final "hack" that we've mentioned before: If you make up water ahead of time, utilizing some form of pretreatment (like reverse osmosis/deionization), add some botnaicals into the storage containers to "pre-tint" the water. Now, I'll admit that this is literally trial and error- and you will simply need to experiment to see what the impact on your makeup water is.
SO, in summary-
*Select materials which are known to impart significant tannin-derived coloration.
*Limit the use of chemical filtration media, like activated carbon (hint- try Poly Bio Marine "Poly Filter- an amazing adsorbant media which seems to not affect "tint").
*Use quantities sufficient to achieve the "look" and conditions you want, and consider doing them slowly and carefully, while gauging the impact of these additions to the life forms in your tank...particularly an established one.
*Continuously replace the botanicals which you are using as they decompose.
*Observe your aquarium carefully and frequently. Test the basic water parameters regularly. Record your results and develop your own regimen/procedures accordingly.
Bottom line: You need to do some experimentation...there are no "absolute dosages" and "simple formulas" to determine how much/how often, etc. to add materials. Just too many variables at play to responsibly do so. That's part of our reason why we question the efficiency/reliabilty of so-called "blackwater extracts" for this purpose. I mean, sure, they probably can be dialed in with a greater degree of accuracy once you're able to test and establish baseline conditions for your tank, but it requires effort and time. I bet that they're not better or worse than simply adding seed pods and such...and at least seed pods have the added advantage o aesthetics and "time release" of tannins as they decompose!
The best we can do is utilize some scientific-influenced thoughts and practices to enhance what is really an art...
And that's not necessarily a bad thing. It just requires work.
Who's afraid of that?
Stay diligent. Stay consistent. Stay inquisitive. Stay observant...
And Stay Wet.