Boosting Biofilter Performance - ALKALINITY - PART 1

Alright, listen up.

We need to have a serious chat.

I see it every day on forums, in Facebook groups, in panicked client emails and in phone calls: an under-performing bio filter and an obsessive, neurotic fixation on pH. Dumping chemicals, not supplementing alkalinity, chasing a "perfect" 7.0 (or less! shudder), and stressing out because their pH crept up to 7.8.

Let me be crystal clear: You are focusing on the wrong thing.

Your obsession with pH is not only pointless, it's actively harming your system. You're treating a symptom while the underlying disease—a starving biofilter—is getting worse. 

Today, I'm going to (hopefully) help you fix this. You're going to learn why alkalinity is the real boss, and why pH is just its loud, unreliable subordinate. 

Strap in a multi-part series on Alkalinity and biofilter performance.

And YES, its important, SO LISTEN UP. 

The CO₂ Factor: Why Your pH Meter Lies to You

Before we go further, you need to understand that your pH reading is easily influenced. The biggest culprit? Carbon Dioxide (CO₂).

Every living thing in your tank—fish, bacteria, even algae and plants at night—is constantly respiring and releasing CO₂. This CO₂ dissolves in the water and forms carbonic acid, which, as the name implies, is an acid. It pushes your pH down.

This happens independently of your alkalinity. You can have a rock-solid alkalinity level (your buffer), but a high fish load can produce enough CO₂ to make your pH read 7.4 or lower. Chasing that bouncing number is a fool's errand.

So if you are control your alkalinity dosing with pH readings, I best be seeing a co2 reading, or at least a chart of the pH, kH co2 relationship being used to get a slightly better idea and calculate it more accurately. 

OR, we could just test alkalinity........ (see the theme I've got going here?)

The Unbreakable Hierarchy: Oxygen, Biofilter, Everything Else

In any aquatic system, there is a non-negotiable hierarchy of importance.

1. Oxygen: No oxygen, everything is dead in minutes.
2. The Biofilter: This is the engine that converts lethal ammonia into nitrate. It is the second-most-important process in your entire system.

If your biofilter fails, your system will crash. And what does this all-important engine run on? Alkalinity. It is the fuel for nitrification. Without it, your biofilter starves. 

The Amateur's Mistake: Lowering pH to "Fix" Ammonia

This is the one that really gets my blood boiling. Your biofilter is underperforming because you've let the alkalinity run out. Ammonia is climbing. You read somewhere that ammonia is less toxic at a lower pH, so you add an acid buffer, or just dont supplment you alkalinity enough leading to a drop in pH. 

This is the single WORST thing you can do.

You've just put a chemical band-aid on a catastrophic engine failure. The point is, in aquaculture especially, a stable pH and KH trumps controlling pH to lower the toxicity of ammonia from an under performing bio filter EVERY. SINGLE. TIME.

Its like blowing a head gasket, draining the fuel tank, and then sitting back scratching your head asking why the car inst running again. 

Your Fish Are Tougher Than You Think

"But G, a pH of 8.0 will stress my fish!"

No, it won't. Most species will happily thrive in a stable pH of 7.5 to 8.2. They will adapt.

What they cannot adapt to is the toxic soup of a failed biofilter.

Yes, of course, some systems need specific parameters, like when conditioning high-value ornamental broodstock. But for the 99% of you, and especially for commercial aquaculture, stop complicating it.

Let's Kill Some Industry Myths

1. Myth: "You can't let your alkalinity go over 100ppm."
   • Truth: Absolute rubbish. In many of our commercial RAS, we aim for 150ppm, 200ppm, or even higher.
2. Myth: "A pH over 7.5 is bad."
   • Truth: A stable pH is a paradise compared to a fluctuating/low pH with an ammonia problem.
     

Your System is Crashing? I Know Why.

Does this sound familiar? You're constantly fighting ammonia spikes. Your pH is unstable, swinging all over the place. You're dealing with mortalities, health issues, and you're at your wit's end.

It’s fun to troubleshoot, and I’ll bet you a carton of your favourite beer—no, I will 99% guarantee—that insufficient alkalinity is the root cause of your problems.

This isn't some secret BTA trick; it's fundamental biology. This is why professional aquaculture pond farmers lime their ponds before filling. They are building a massive alkalinity reserve from day one. They then supplement with bicarbonates, carbonates, or hydroxides when needed to keep that biofilter engine humming along. They are proactive, not reactive. (and yes, they are testing alkalinity to determine this, not pH. 

If your system is a constant headache, stop guessing and stop wasting money on fish. Let's fix the real problem. Give us a call, send an email to info@btaqua.com.au , or drop a comment below. We'll get you sorted.

The Final Word (For Now)

Let's recap, so there are no excuses.

1. Focus on Alkalinity (KH), not pH. Your pH reading is a fickle liar.
2. Feed your biofilter. Keep your KH stable. This is non-negotiable.
3. Do not chase a "perfect" pH number. Stability trumps a specific number.
4. Never lower your pH to manage an ammonia spike. You're only making it worse.

Once you become familiar with your species and master your water chemistry, you can adjust and control alkalinity as you wish. But first, you must master the fundamentals.

In Part 2 of this series, we'll go over the specific supplements in detail, discuss target alkalinity levels for different systems, and analyze the critical relationship between your buffer additions and your source water.

Now go test your KH. Don't make me come over there!

P.S. Still not convinced? Let me spell it out for you.

Your biofilter also hates low pH.

So, allowing your alkalinity to drop to lower pH does two things simultaneously:

1. It starves your biofilter of the fuel it needs to process ammonia and nitrite (alkalinity) 
2. The resulting low pH further stresses both the fish and the biofilter, creating a death spiral until the whole system crashes.

Your fish then have to constantly fight the difference in pH between their internal organs and the water outside, adding massive osmotic stress to their already poisoned bodies.

Lowering pH to "treat" ammonia toxicity is putting band-aids on bullet holes.

This is biological chemistry, not witchcraft. Once you harness it, you will realise the only thing you were impacting by lowering the pH was your fish's health—negatively.

Be nice to your fish. It's the least we can do, considering we are going to eat them.

...and, AND!!!!!!

Your system will actually perform better, your fish will be healthier and grow better. 

#BTA #aquaculture #aquarium #biotechaquatica #alkalinity #pH #biofilter #waterquality