The 24-Hour Test That Proves Your Cloner Is Sterile

Ask ten growers if their cloner is sterile and ten of them will say "yeah, I cleaned it." Cleaned it. That's a feeling, not a fact. I spent years chasing mystery failures. Slimy stems, stalled roots, a reservoir that smelled fine on Monday and like a swamp by Friday. Eventually I admitted the truth: I didn't actually know if my system was sterile. I was hoping.

Hope is not a protocol.

So I built a test to replace it. It costs about a dollar in pool strips, it runs while you sleep, and it hands you a real pass/fail. I call it the oxidizer baseline, and once you run it you'll never clone blind again.

Sterility is a number, not a vibe

Here's the whole trick: free chlorine gets consumed by organic life. Bacteria, fungi, and biofilm all eat oxidizer. Clean water doesn't. So if you put a known amount of free chlorine into your system and it stays there, nothing is eating it. And nothing eating it means nothing living in it. That's your proof.

Temps matter, nutrients matter, lighting matters. But none of that fixes a cloner seeded with biofilm, and none of it tells you whether you have one. This test does.

Running the baseline

Step 1: Start from a clean slate. Fully sterilize the system first. Circulate 3–5 mL/gal of 8.25% bleach overnight (8 to 12 hours), then dump. Do not rinse. Low-dose oxidizer over a long exposure dissolves biofilm far better than a quick high-dose shock. That's a hill I'll die on.

Step 2: Refill and spike. Fill with your normal cloning water. Add 0.2–0.3 mL/gal of bleach (about 4 to 6 drops per gallon). Circulate a minute to mix, then read your free chlorine with a pool strip and write the number down.

Step 3: Wait 24 hours, then read again.

• Free chlorine still reads 1–3 ppm means PASS. Your system is sterile. Nothing organic is in there consuming it, so go clone.
• Free chlorine dropped toward zero means FAIL. Something living is eating your oxidizer. You are not sterile, no matter how clean it looked.

When you fail (and most people fail the first time)

Don't panic. Failing the first baseline is normal, especially on a system that's been running a while. Re-spike another 0.2–0.3 mL/gal and wait another 24 hours. Keep re-spiking daily until it finally holds for a full day.

• A mildly contaminated system usually holds after 1 day.
• A heavily colonized one can take 2 to 5 days of daily re-spikes.
• If it never holds, you don't have a chemistry problem. You have a workflow problem. Something in your routine is re-seeding the system every time you touch it. (That's a whole other article, and it usually comes back to one hidden pump part.)

Why use plain bleach for the test

Because pool strips read hypochlorite accurately, and bleach is hypochlorite. Fancier oxidizers work great in the cloner, but they don't all read cleanly on a strip. For the baseline test specifically, bleach gives you the trustworthy number. Use free-and-total chlorine strips. The cheap ones from any pool aisle are fine.

The payoff

Once you can prove sterility instead of hoping for it, the whole game changes. Rooting speeds up and the random failures stop, because you've removed the one variable that was quietly wrecking your cycles. You stop treating cloning like luck and start treating it like the repeatable, boring, dependable process it's supposed to be.

Run the baseline once and you'll understand why I say it: get sterile, get cloning.

Questions about your own baseline reading? Reach out through the contact form. I read every one.

Michael Goldsmith, PermaClone.com

#GetSterileGetCloning