We talk a lot about establishing more natural-functioning/appearing systems, and many of the nuances associated with getting them up and running. And of course, we talk a lot about how to manage these systems for the longer term.
However, we seem to spend a relatively small amount of time talking about what happens in these tanks over the very long term, right? With so many hobbyists getting into this style of aquarium for the first time, it's worth another look!
So, I thought I'd touch briefly on some of the things I've noticed in our blackwater, botanical-style tanks over the long term, and how the regular maintenance tasks we engage in affect their function and overall health.
First off, there are some characteristics of these types of tanks which require a fair amount of continued management that keep them functioning as blackwater tanks; most notably, the continuous addition of more botanical items to replace those which break down, be they leaves, wood, or seed pods and the like- in order to maintain not only the visual "tint", but the beneficial humic substances and other organics contained in these materials.
Over time, many of these compounds are dissolved into the water column, and these botanical materials will no doubt lose some of their efficacy as "environmental enhancers."
And obviously, this sort of "active management" not only creates a more stable environment for your fishes, it provides an opportunity to continuously engage with your aquatic environment on a very regular basis. This process is one of the most important aspects of managing any aquarium, but is especially critical in an environment in which the very structure of the aquascape itself evolves and changes over time!
Now, unlike other tanks I've managed over the years, such as reef aquariums, planted tanks, etc., where you need to sort of change or evolve your husbandry tasks as the tank ages (i.e.; pruning, revising fertilization schemes, etc.), the botanical-style blackwater aquarium seems to benefit from the same types of maintenance tasks throughout its functional lifetime. Some hobbyists choose to let their botanical items remain in the system until fully decomposed; others prefer to remove items just as soon as they lose the "pristine show look." Regardless of how you handle the "botanical breakdown", you're more-or-less following the same practices over a long term.
And of course, water exchanges are as important a part of the management of our systems as any other. The dissolution of organics and "reset" that water exchanges provide are one of the "cornerstone" practices in aquarium husbandry, and will help continuously hold your environmental parameters.
As any aquarium ages, it's essential to at least have a handle on what is happening chemically. In the botanical-style, blackwater aquarium, it's nice to conduct basic water parameter tests early on in the tank's existence, to establish a reference "baseline" of the tanks typical "operating parameters". In a typical tank, you often see a gradual reduction in pH over time. This may be caused by acids forming from accumulated nitrate and other nitrogenous compounds and over time, as they overwhelm the buffering capacity of the tank. This seems to be much more common in higher pH systems, such as African cichlid tanks, reef aquaria, etc.
You will likely find, as I have, that with the consistent management of your blackwater tank, very little in the way of "parameter shift" appears to occur. I've seldom noticed any sort of appreciable pH decline over time in these tanks (probably because you're starting out with lower pH!), and nitrate and/or phosphate levels tend not to vary significantly at all with consistent botanical replacements and water exchanges.
I'm curious what YOUR experience has been in this respect.
I also tend to monitor TDS a lot in botanical tanks, and I've found that I will see a "range" of 2-3 ppm at the most, in which the parameters seem to stay throughout the lifetime of the tank. Any deviation from this should be something that you should investigate. Not necessarily a "bad" thing, as TDS can be just about anything...yet it does function as a sort of "yardstick" for environmental consistency.
One physical maintenance task that I have found to be continuous and necessary is the cleaning of filter intakes, mechanical filter media, and water pumps. With a constantly-decomposing array of botanical materials streaming into the water column, lots of small debris tend to get sucked into filter intakes, pumps, and of course, mechanical filter media. These need to be cleaned/replaced on a regular basis; perhaps even more frequently than other maintenance tasks. It's simply part of the game when working with a botanical-style blackwater aquarium!
Nothing we've mentioned here is earth-shattering or revolutionary, from an aquarium husbandry standpoint. However, seeing that for many hobbyists, this is their first experience at managing a botanical-style blackwater aquarium, I think it's not a bad idea to review this sort of stuff from time to time. Seldom are big moves or corrections required. Rather, it's really a combination of little things, done consistently over time, which will see your aquarium thrive in the long run.
Stay consistent. Stay active. Stay observant. Stay involved.
And Stay Wet.