Read Your Water Like a Chemist: Pool Strips for Cloners

The most useful diagnostic tool in cloning costs about a dollar and lives in the pool aisle. A chlorine test strip. Most growers either don't use one or don't know how to read the one they have, which is a shame, because it turns sterility from a guess into a number.

Let me teach you to read it like a chemist.

Free chlorine vs total chlorine

A good strip reads two things, and the difference between them is where the real information lives.

• Free chlorine is the active, available oxidizer. This is the stuff still working, still able to kill microbes. This is the number you care about most.
• Total chlorine is free chlorine plus combined chlorine, the portion that has already reacted with organic material and been used up. It's spent oxidizer that's still hanging around as a compound.

When free and total read the same, all your chlorine is active and unspent. When total is higher than free, some of your oxidizer has already been consumed by organic load. That gap is a clue.

What the numbers mean for a cloner

Here are the targets to read against, all in free chlorine:

• 2 to 4 ppm is the water-treatment range for unrooted cuttings. This is safe for tissue and it's roughly what municipal tap water is treated to, so it's a proven-safe zone.
• 0.5 to 2 ppm is where you drop to once callus and roots have formed, since rooted tissue wants a gentler dose.
• 1 to 3 ppm held for 24 hours is your proof of sterile. That's the oxidizer baseline: spike it, wait a day, and if it still reads 1 to 3 ppm, nothing organic is eating it.
• Zero means either you never dosed or something consumed it all. On a system you spiked yesterday, zero is a failing grade.

Why bleach reads best on a strip

A quick but important note. Pool strips are calibrated to read hypochlorite, which is exactly what household bleach is. So for testing, bleach gives you the most trustworthy number. Fancier oxidizers like peroxide or peroxyacetic acid work beautifully in the cloner, but they don't all read cleanly on a chlorine strip, so don't try to judge those by the same test. For the baseline specifically, dose with bleach and read with confidence.

Reading the gap in practice

Say you spike to 3 ppm free and, an hour later, free reads 1 ppm while total reads 3 ppm. That gap tells you something in the system just consumed 2 ppm of oxidizer in an hour. That's a live organic load, and it's the early warning that your system isn't as clean as it looks. A clean system holds the gap near zero and the free chlorine steady.

Once you can read the strip, you stop flying blind. Every dose becomes measurable, every sterilization gets a pass or fail, and the guesswork that makes cloning feel like luck just falls away.

Not sure how to read your own strip result? Send me a photo of it through the contact form.

Michael Goldsmith, PermaClone.com

#GetSterileGetCloning