It's Saturday. No coffee-fuelled rant this week — just a quiet cup of tea, a still morning, and one small piece of knowledge worth passing on slowly. Sit with it a moment.

Last week we spoke about bacteria being the workforce of every aquatic system on earth. This week, one number: CFU — colony forming units. It is the number that tells you whether the workforce you just bought is a crew of ten or an army of ten billion. Knowing it is not complicated. It is a single piece of information, and it changes everything about how you choose, value and dose a probiotic.

So you have found the number on the label. Now — how do you read it? Because a label will not hand you fifty billion in plain words. It hands you something like 5 × 10¹⁰ CFU/g, and expects you to know what that means. Let us slow down and read it together.

A CFU count is almost always written in scientific notation — a shorthand for very large numbers. It has two parts: a multiplier (the small number before the ×) and a power of ten (the small raised number after it). The power of ten tells you how many zeros to add. The multiplier tells you how many sets of that size you are holding.

10⁹ means a one followed by nine zeros — one billion. 10¹¹ means a one followed by eleven zeros — one hundred billion. The multiplier in front simply says how many of those you have:

And notice what the notation lets you see at a glance: 5 × 10¹⁰ is five times larger than 1 × 10¹⁰. 1 × 10¹¹ is ten times larger than 1 × 10¹⁰. When the powers of ten match, compare the multipliers. When they do not, each step up in the exponent is another zero — another factor of ten. This is why the notation exists: not to confuse you, but to let you compare armies of billions with a glance.

Walk to the shelf — physical or digital — and look at the probiotic aisle. "Concentrated blend." "High potency." "Professional strength." Lovely words. Quietly, completely, meaningless.

"Concentrated" compared to what? "High potency" measured how? "Professional" according to whom?

Marketing language cannot be compared. CFU can. 5 × 10¹⁰ CFU/g is exactly half the strength of 10¹¹ CFU/g — every time, no interpretation required. It is the one number in this industry that places every product on the same ruler.

And it is not only about strength — it is about what is in the blend. A product with 24 strains at 5 × 10¹⁰ CFU/g and a product with 3 strains at the same count are very different tools. The CFU tells you the size of the workforce; the strain list tells you which trades are on the crew. You need both. But without the CFU, the strain list is only a guest list for a party you cannot be sure is happening.

And this is the one that matters day to day. Dosing a probiotic without a CFU count is guesswork wearing the costume of a routine.

Consider what a dose actually is. When you add a bacterial supplement to an aquarium or a pond, what you are really adding is a number of viable bacteria into a volume of water. The natural way to express a dose is bacteria per litre. And there is no path from "a scoop" to bacteria per litre without knowing the CFU/g of the powder in the scoop.

It flows both ways, like water does. When we publish a dose rate on a BTA label, that rate is calculated backwards from a target bacteria-per-litre number using the actual CFU of that batch. Change the CFU and the correct scoop changes with it. The dose rate and the CFU are one number wearing two coats. Any seller who publishes dose rates but not CFU counts is asking you to trust maths they will not show you.

So the CFU count is not just a number for comparing bottles. It is the tool you use to manipulate the dose rate itself. You take the CFU/mL (or CFU/g) of the product, and you work backwards from the concentration you want in your water to the grams or millilitres you add. That is lever one.

Lever two is frequency. Twice weekly, once a week, once a fortnight — the frequency you dose is adjusted to your system: its stocking density, its filtration, its water exchange, its stress levels. Two levers, both in your hands, both calculated from the same number on the label.

And we can show you how to do this, because we have done the work: we have a calculator, and we have spec sheets showing different CFU/mL dose rates and their corresponding dose rates for every microbial product we sell. You do not have to guess. You tell us your system, we show you the maths.

Notice what that example just did. The dose rate was not chosen by the size of the bottle — it was chosen by what the system is and what we want it to do. In the pond we want the bloom, so we never dose a nutrient-stripping blend like Microplex that would outcompete the phytoplankton — we dose a sludge-digesting, nutrient-liberating blend like SUB-6, because the bloom is the oxygen and the filtration. In the RAS we want nutrients stripped, because the machine does the oxygen. Same environment, opposite strategy — and the CFU count is how we set both.

And when you dose like this — strains matched to the job, rate and frequency set to the system — you will notice it: reductions in ammonia, nitrite and nitrate with the right blends, reductions in solid waste with the blends built for it. That is the whole practice in one sentence: know the strains, know the count, set the dose, set the frequency. That is how you quantify the value in a microbial product — especially ours.

It would be a strange lesson to teach label honesty and then hide our own numbers. Every BTA microbial product states its viable count. Here is the current range:

Notice they are not all the same number — because they are not all the same tool. Microplex is a broad 24-strain workforce for general stability. PMX-8 is the concentrated settler for serious biosecurity support. Nitroplex is a nitrogen specialist. SUB-6 is a pond and planted-system specialist. The CFU tells you the size of each crew; the strains tell you what each crew does. Both numbers, every label, every time.