With all of the leaves and botanicals we toss in our tanks, how do we keep those tinted microcosms from becoming algae-smothered, green water swamps?
A very good question...And you might be surprised to learn that massive algal growths in blackwater/brackish botanical-style aquariums are surprisingly uncommon, in my personal experience. Yes, despite all of the decomposing leaves, seed pods, and wood, you can still keep a botanical-style blackwater/brackish tank clean and with minimal visible algal growths.
The keys are pretty much like those you'd expect from managing any type of aquarium, really. They're all rooted in the basics of aquarium husbandry. And the backbone of any aquarium maintenance regimen is (wait for it...) water exchanges!
I am a big one for weekly 20% water exchanges.
i have been a water exchange proponent since the dawn of my fish-keeping days, and I think it's the single most beneficial practice any hobbyist could employ to keep an aquarium healthy over the long term. In our botanical-style, blackwater aquariums, it's an essential part of the game, and should be "baked in" to our system management practices.
And of course, the source water is important- you want to use high-quality water (I'm a huge fan of RO/DI systems) to complete these exchanges. You can steep a few leaves or botanicals in the water storage containers you use, to get the "visual tint" and chemical characteristics you are looking for.
And yes, the other key ingredient for long-term success with a botanical-style blackwater/brackish aquarium is to go slowly...Stock gradually and at a lighter level than you might want...at least in the early phases, as this gives the beneficial bacterial populations the chance to adjust to an expanding fish population and bioload of decomposing botanical materials.
I am also a huge fan of using chemical filtration media on a regular basis, not only to "scavenge" organic excesses, but to provide an extra layer of protection against the occasional lapses in husbandry that befall every hobbyist from time to time! And no, if you just use a little, you won't be removing the "tint" you're so carefully trying to cultivate- trust me. Every tank I set up has some sort of chemical filtration media, and no one could accuse me of having "clear blues-white water" in MY systems!
And of course, with fish populations comes the need to feed...and you will need to simply utilize those common careful feeding practices that you'd employ in any style of aquarium. One thought I've had about our botanical-style tanks is that they encourage fishes to graze on biofilms and yes, some of the algal films which might form on wood and other materials over time. So surprisingly, I feed my fishes a lot less frequently (like once a day) than I used to, and they're none the worse for it!
Again, stocking over a period of months before you achieve complete "fish population density" is not some high-concept thing, but I think it's so key to success. And it incorporates our mindset of patience above everything else. And everyone can do this...right?
Back to stocking for a second...this refers to both the fishes AND the botanical materials you're using in your 'scape. You don't have to start of all maxed-out with leaves and seed pods and such.
Sure, get started with a nice selection of materials to get your tank off to a good aesthetic start, but realize that you'll no doubt "edit" both the look and "botanical population" of your tank as it evolves- as you get a feel for just how you want it to look and operate over time.
And trust me, your ideas will evolve just like your aquarium, and you'll be "editing" as you go- working the tank gradually towards some look you're trying to achieve- some environmental parameters you're wanting to give your fishes...It's part of the game here!
And you'll be regularly replacing/adding to the fish population and botanical 'populations" as they break down. And guess what? Nature will dictate the pace. Just like in everything else.
The key is to be patient...and to keenly observe what nature is "advising" you to do with your aquarium.
Common sense. Patience. Observation. Basic aquarium management skills. They're all required. Nothing earth-shattering here.
Stay patient. Stay observant. Stay consistent...
And Stay Wet.