Boosting Biofilter Performance - Your pH is a Liar, Part 2: Bulletproof Buffering - And dissolved minerals (gH)

Alright, settle down...

Grab a tea, coffee, bonox, redbull, whiskey or a cold stubbie and lock in, we are talking about buffer choice, and why it matters. 

You survived Part 1. You've stopped chasing pH like a headless chook and you've finally understood that alkalinity is the fuel that runs your biofilter's engine. Welcome to the next level.

Now that you're not a rookie anymore, we're going to open the toolbox. Because blindly dumping in any old buffer is just as harmful as ignoring alkalinity in the first place. The buffer you choose is a strategic decision, and it all starts with one thing you've probably been ignoring: your source water.

Step 1: Know Your Water. And Keep Knowing It.

Before you add a single gram of anything, you need to know what you're starting with. This is non-negotiable. Go test your source water—whether it's from the tap, a river, a bore, or a rainwater tank—for two things:

1. Alkalinity (KH): The fuel for your biofilter. Also known as Carbonate Hardness or Temporary Hardness because it doesn't hang around.
2. General Hardness (GH): The measure of dissolved minerals. Also known as Permanent Hardness (while its not "permanent" it sticks around for a lot longer)

So how often should you test your source water? A good rule of thumb is twice a year. However, you need to be smarter than the calendar. You must also test:

• IF you notice changes in your system's performance or your fishes' behaviour.
• AFTER a major weather event. A drought can concentrate minerals in your river or bore water. A flood can dilute everything or introduce new contaminants. If your source water changes, your strategy must change with it.

The "Big Three" and Why Your Fish Crave Them

The "Big Three" essential minerals for fish health are Calcium, Magnesium, and Potassium. They are non-negotiable requirements for life. When you manage your GH, you are managing the building blocks of your fish.

• Calcium (Ca): This is the rebar in their bones and the armour plating on their scales. It's the spark for every muscle contraction and nerve impulse. 
• Magnesium (Mg): Think of magnesium as the master key for their metabolism. It unlocks hundreds of enzymes responsible for turning food into energy. No magnesium, no energy. It's that simple.
• Potassium (K): This is the bouncer at the door of every single cell. It manages osmoregulation—the critical balance of water and salts inside the fish versus the outside world. Without proper potassium, your fish are under constant osmotic stress, burning energy just to stay alive instead of growing.

The Strategy: From Simple Scenarios to Complex Reality

What if your water has some minerals but not others? What if your river water is high in calcium but has zero magnesium or potassium?

This is where you graduate from being a water-keeper to a water-chemist. Change it up as dictated by your water. If your water is high in calcium, you'd use a potassium-based buffer like Potassium Bicarbonate to raise your alkalinity while adding essential potassium. You could then supplement magnesium separately.

Over time, you can identify what you need by how your fish behave (and yes, the signs can be subtle). For those who want to go deep, you can get your water tested with an ICP test (we recommend Triton Applied Reef Bioscience). It's not required all the time, but it can give you a crystal-clear picture of what's going on.

Fuel vs. Oil: Why KH and GH Behave Differently

• Alkalinity (KH) is consumed rapidly. It's the fuel your biofilter burns every single day.
• General Hardness (GH) sticks around. Your mineral levels are mostly influenced by dilution from water exchanges and backwashes, much like how salinity gets diluted over time.

This means you can be strategic. Say your water has gotten too high in minerals from constant buffering. What do you do? Swap to cheap, good old Sodium Bicarbonate or Sodium Carbonate for a while. You'll keep the biofilter humming, save some cash, and know your fish are still getting all the minerals they need from the water. Then watch the growth.

I'm not saying you need to test for every mineral each week, then get the abacus out, create a custom blend, yell a bit, keep testing, yell a bit more (possibly some swearing), run outside (probably while swearing a bit more) and shake your fist at the sky and say WHY DID I LEARN THIS!!!!!!!!!. 

No. I'm saying: know your source water, adjust as necessary, and let your fish tell you what they need. You'll avoid overshooting one mineral or another, and you'll find your system runs a lot better.

The BTA Benchmarks: Target Numbers for Your System

• General Hardness (GH): Aim for 100 - 200 ppm (about 6-12 dGH). (Freshwater only). higher is acceptable but can create issues (calcium deposits for instance), youre the boss, youll be able to tell. 
• Alkalinity (KH): Aim for a robust 80 - 150 ppm. (Saltwater is maintained around 150-180ppm). remember, the more alkalinity you have, the more reserve you have before things start going wrong. 
• Expected pH: With these levels and a moderate biological load (producing 10-15ppm of CO₂), expect your pH to naturally sit between 7.4 and 8.0, and thats fine!

The Armoury: Choosing Your Weapon

This isn't an exhaustive list. There are other buffers out there, each with their own quirks, but they can all be made to work if you know what you have, and what you don't have, in your water.

• Sodium Bicarbonate: Gentle, doesn't result in as high of a pH, and dissolves quickly. The reliable workhorse.
• Sodium Carbonate (Soda Ash): Results in a higher pH than bicarb and is relatively quick to dissolve.
• Sodium Hydroxide (Caustic Soda): A LOT of alkalinity and a very high pH. It's caustic, so handle with care. It's very easy to overshoot your pH with this. It strips CO₂ from the water to create bicarbonates from hydroxides. For pros on large systems.
• Calcium Carbonate (Aragonite, Shell Grit): Slow dissolving. Usually needs a pH below 6.8 to dissolve effectively and works more readily in freshwater.
• Dolomite (Calcium Magnesium Carbonate): Slow dissolving, but can be a great source of slow-release calcium and magnesium in freshwater systems.
• Potassium Bicarbonate: The hero for Aquaponics. Results in a lower pH than carbonate or hydroxides, creating a stable pH and KH at any alkalinity level. It's fast dissolving and adds essential potassium to the water.
• Potassium Carbonate: Same as potassium bicarbonate, but results in a slightly higher pH.
• Magnesium Buffers (Carbonate, Bicarbonate, Hydroxide): For water low in Magnesium. These can be expensive; it is often cheaper to simply supplement magnesium with Magnesium Chloride or Magnesium Sulphate (Epsom salt).

The Final Word: You Are a Waste Treatment Manager, above all.

Remember, fish not only live in their home, they drink it. It absorbs into their bodies through osmosis. These are not grazing cattle; they can't just drop a deuce on the ground and walk away from it and not have to worry about it, especially in a closed system. 

Fish don't have great hygiene, they dump their waste non-nonchalantly into the same water they live in, drink from and breathe in, they dont care.

Your job is to take care of the fish and the water. If we plan to grow these things effectively, you have to not only feed the fish, but you have to actively clean up after them every single day. That cleanup is driven by your biofilter, and your biofilter is driven by alkalinity.

Stop guessing. Start thinking.

OH, and dont forget the salt!

Sodium chloride is good, and stuff. 

P.S. Dont forget the Boys at Triton for the in depth water analysis, Eshan and Julian are good eggs!

https://www.triton-lab.de/

#BTA #aquaculture #aquarium #biotechaquatica #alkalinity #waterchemistry #buffer #GH #KH