#i have plenty of literature from the 90's to the 00's that stress the importance of keeping acidic fish in acidic environments

[anabantoid]

Altering pH, what's it for, how do you do it?

We've heard it a lot before, "I don't need a certain pH, I just need a stable pH" and we've never questioned it. And why should we? What is pH, the measured scale of acidic to alkaline, and how does it effect the lives of our fish in the aquaria and outside of it? 

First let's start off with what it is. As mentioned above, pH is a scale with which you measure the acidity or alkalinity of a liquid, your soil, even some parts of your body, and more. Here's a good chart.

Here’s the short and sweet version:

You can’t just dunk in a bunch of pH down to lower your pH, or you’ll cause the pH to drop, then rise back up, and kill your fish.

You have to determine your kH and pH from the tap

High kH will prevent your pH from being lowered because of its high buffering capabilities, low kH will make your pH swing wildly because of its lack of buffering capabilities

Play around with altering your water in an unstocked tank to get a feel for the procedure and how much remineralizer to use or chemical buffers to use without harming your fish.

RO/DI will give you water with 0 kH and 0 gH. Use Salty Shrimp gH/kH+ to remineralize. A kH value between 4-6 will allow you to safely alter your pH without it swinging. You need to add gH because it contains essential minerals fish and plants need to live.

Use botanicals, such a leaves (refer to the charts!) or seed pods, to release tannins and lower the pH OR you can use an active aquasoil (refer to the paragraph above for the pros and cons and further explanation).

You can also use chemical buffers like acid buffer from Seachem that will soften your water (lower kH) and allow for your pH to be adjusted, or you can use neutral regulator the same was as it brings your pH to 7 and softens the water.

Stock accordingly, check your kH, gH and pH often to make sure it’s all correct and stable.

Have fun!

Here’s the long and meaty version:

In the wild, there's multiple factors that lead to waters being more acidic, more neutral and more alkaline. In Amazonian rivers, as well as peat bogs in Indonesia, the concentration of decaying organic matter like leaf litter and wood releases tannins.

Tannins are an organic compound found in plants, and in some trees the tannins help prevent predation from insects, as well as operating as an antimicrobial and antifungal. When the parts of the plant fall into the water, the tannins are leached out and released into the water, which alters the water's chemistry by making it more acidic, and over time, softer. This is what gives peat swamps and the Amazon their rich, dark colored waters, and makes them soft and acidic. Another friend that helps out with this is humic acid, molecules present in plants that help them receive nutrients. Blackwater is filled with tannic and humic acids because of the decaying plant matter!

In reverse, the minerals in bodies of water will alter its chemistry. Karstic lakes are bodies of water carved into dolomite, limestone or gypsum, which are all rich in hard water causing minerals like calcium carbonates, and those minerals in turn can make the water very hard and alkaline.

We all agree that Rift Lake cichlids and saltwater fish need a certain water chemistry, they've evolved to live and flourish only in those water conditions, and taking them out long term can be detrimental to their health and cause illness and shorten their lifespans. Fish that evolved to be acidophiles evolved a specific way for a reason, and a few generations in captivity doesn't change that. In fact many breeders don't breed in hard water, but soften their water using RO/DI for these acid loving fish, and raise them in these conditions. This is why when you bring home cardinal tetras, you see a massive die off because you're taking fish kept in neutral to below neutral waters and adding them to a tank that had your tap with a pH of 8 and it shocks them and kills them.

Okay, great, you're thinking, you told me a bunch of stuff but haven't told me how to change my pH.

In order to to adjust your pH, you need to know your kH (carbonate hardness). It's the carbonate hardness that determines your pH in MOST situations (Sulawesi need not apply, the waters there are soft but the pH is alkaline!).

My friend @justnoodlefishthings can explain it way better than me: "Carbonate hardness, or kH, is the measure of calcium carbonate in the water. Calcium carbonate will dissociate into calcium and carbonate ions in water. The carbonate ions are unstable and unhappy and thus will readily suck up all available hydrogen ions in the water. The more hydrogen ions you have in water, the more acidic it is and vice versa for basicity. So, if you have a high kH, then there are not a lot of H+’s floating around to make the water any more acidic than what it already is. This prevents the pH from swinging wildly in any direction."

What this means is that it's crucial to know your kH in order to adjust your pH. You can't just add tannins and go "well that should do it!", otherwise you'll get alkaline tea water.

This is the range you're looking for when altering: 4-6 kH. The higher you get, the harder it is to lower your pH, and the lower you get, the more your pH will swing randomly without the buffering capabilities of your kH. That means your pH can swing to bother very acidic levels, like a peat swamp, or very alkaline levels, like a Sulawesi lake, despite having no kH.

Alright, so then how do I actually do it?

After testing your tap and determining your starting pH and kH, and you know you wanna keep specialized acidophiles, you realize you gotta do something. Your kH is reading at 8 and your pH is reading at 7.8, both of these things are the opposite of what you need. How can you fix this?

The safest is way is by getting RO/DI water from your LFS, or investing in a system of your own. They're not expensive compared to other tank equipment, roughly $60 can get you a nice RO Buddy off of Amazon. Your LFS prices may vary, but my advice is to get about ten gallons of RO from your LFS (it'll usually be $10-$15) and you can always try out altering the tank before getting any stock and seeing how you feel about this. You need to remineralize the RO/DI water, Salty Shrimp gH/kH+ is what I recommend so that you can have some kH for its buffering and stabilizing properties, and you need to add gH back into your tank. gH, calcium, magnesium and other minerals, are vital to fish and plants and all bodies of water contain varying amounts. 

Remember, you want your pH low, but stable, so aim for that 4-5 kH sweet spot. You can play around and get used to mixing the water and finding out your ratios before worrying about if you'll harm your stock if you do this with an empty tank. 

Adding botanicals to your water once it’s at that sweet spot will bring and keep your pH down. Botanicals would be any organic matter that releases tannins and humic acid; leaf litter, seed pods, coconot coir, etc. Here’s a fun chart that shows the different leaves you can use (and you can collect yourself) as well as the tannin outputs.

And this is how those leaves can effect your water.

(From here, also a good article expanding on botanicals and how to collect them yourself)

You can also peruse the catalog of Tannin Aquatics to get some fun things, but be aware that seed pods do eventually rot and you’ll want to periodically pull them out if you notice it being a bit too funky. A slight sulfur smell is okay, that’s the organic material breaking down, but if it smells like rancid farts you’ll want to cycle it out with a new pod.

Another, more expensive route, is to use an aquasoil with your RO/DI water. Aquasoils are things like ADA Amazonia, UNS, Fluval, etc. They’re clay-based, high CEC (cation exchange capacity) which means they’re excellent for your planted tanks. They absorb nutrients from your water and hold onto it so that your plants can use it continuously. It’s also an active soil, it will buffer your pH to around 6 and keep it there without needing to use an additive to raise your kH, but you will need to raise you gH, which would be your calcium and magnesium and other minerals that are vital to fish and plant health. There’s downsides beside the cost; they leech a lot of ammonia when you add them, and can take a month to subside, though this aids in starting a cycle. They will break down over time and turn into mud, and you can’t disturb the soil or have digging fish otherwise they’ll generate massive mud clouds. They also eventually need to be replaced every two years or so, and if you’re like me you don’t like the idea of needing to break down a tank every two years. This is, however, a good option if you’re okay with the above downsides.

You can also use chemical buffers to do all of this work, acid buffer will break down your kH and create co2, and allow for your pH to drop, neutral regulator will soften your water the same way but keep your pH, well, at a neutral 7. I’ve used acid buffer successfully, you just need to follow the directions on the bottle, but you can also experiment with this the same way you would with the RO/DI water.

Remember this, though, below a pH of 5, most bacteria that aid in the nitrogen cycle are unable to live because of the highly acidic conditions. In these extremely low pH environments, they’re peat bogs typically, and peat bogs have one important kind of plant that makes it a peat bog; the sphagnum moss. The sphagnum acts as the beneficial bacteria in this situation, as it takes in the ammonia and nitrogen the bacteria typically would, and uses it up, eliminating it from the water. This is how low pH peat bogs and swamps “cycle” themselves! And why leaving the sphagnum moss alone in these places is important, because they’re the very livelihood of the swamps and bogs. You can always obtain sustainably grown sphagnum moss if you’re looking to replicate a peat bog of your own and allow it to float on the surface in a mat of other mosses, leaves and organic matter, just like you’d see in a real bog.