A question we receive frequently around here is, "How do you keep your water 'clean', in addition to water changes, yet still keep the 'tint' you rave about some much?"
The answer is coming. But first, let's consider a couple of things.
Do you use activated carbon in your aquarium?
Long championed by those who love crystal clear water without any colors or visible impurities, activated carbon does a remarkable job removing organic compounds, acids, and in particular, two substances which accumulate in water- phenols (decidedly nasty substances), and tannins, which....whoah. Wait a minute.
We like our tannins around here, right?
So, why would we want to use carbon?
Well, it's a bit of a conundrum, isn't it? We want some of the other benefits of carbon without what we in the "tinting" world would consider to be a drawback- the superior ability that carbon demonstrates for removing tannins! Activated carbon can increase pH slightly when new, but this is typically a temporary effect. And of course, there are times in aquarium keeping when the immediate need to improve water quality outweighs the "setback" of removing the tannins which tint our water (for example, in an emergency situation where you've overdosed the tank with something, experienced cloudy water, etc., etc.)
Other media, such as Seachem Purigen, also remove tannins, but tend not to affect the ph of the water...so if you like a lower pH environment but are not a fan of the tint (gasp!), you'd be advised to use this media in place of activated carbon. It does eventually become exhausted, and may be regenerated if desired. Better.
Still, that's not totally comforting to us lovers of "the tint"; I mean, that stuff is good. REALLY good! As you may know, we utilized both of these media during our recent "clear water" trial in our office aquarium, and are both happy and sad to report that they kept the water as "colorless as glass" during our (agonizing) two month test run!
What to do? "What do YOU use, Fellman?"
Worry not. Here's the answer.
Seachem makes another wonderful filter media which can do the trick. It's an "organic scavenger resin" called "Renew."
"Huh, what's THAT", you ask?
"Organic scavenger resins" are polymers (resins) that react with specific by-products, impurities, or excess reagents produced in a reaction. In other words, they remove some things and not others. Perfect! Renew will not aggressively remove tannins and humic acid. It will remove organics and particulates and will also help control ammonia, nitrates, and phosphates. Being less aggressive than carbon, it's well suited for tinted tanks and planted aquaria, because it leaves the color bodies and trace elements required by plants present! It is effective for about 30 days, after which time it needs replacement.
This material won't raise the pH of our water like carbon can. Renew allows for control of organics without total depletion, as with more aggressive media such as carbon, etc. The "dose" is 250 mL for each 120–160 L (30–40 US gallons) of aquarium capacity. For a tinted aquarium, it's the only media you need to use on a continuous basis, from my point of view. It almost looks like a an aquarium substrate to me!
So, the answer to the burning question, "What's the most useful chemical filtration media in a tannin-stained aquarium?" in my humble opinion, is Seachem Renew. I love the stuff, and I've been using it for some time. The next question is, "Will you be selling the stuff?" And the answer is, "We sure will!" Look for it on the site now as our "media of choice" for the tinted aquarium!
So, go ahead and add those leaves, throw in that wood, and a few seed pods while you're at it...and know that your tank is protected from excessive accumulation of organics by this efficient organic scavenger resin!
It's often interesting to look beyond the immediately obvious choices, and then find things that really work for us. Use of an organic scavenger resin is the ideal compromise, in my opinion, between necessary utility and aesthetic considerations!
Stay focused. Stay thoughtful. Stay open-minded.
And Stay Wet.