Balancing electrical conductivity (EC) is the secret sauce behind lush, fast-growing hydroponic crops. Too high and you’ll scorch roots; too low and plants starve. Follow the steps below and you’ll keep nutrients dialled-in like a pro—no chemistry degree required.
What EC Actually Tells You
EC measures the total salts (ions) dissolved in your reservoir. The reading is expressed in milli-Siemens per centimetre (mS/cm). A higher reading = stronger feed, while a lower reading = weaker feed. Most leafy greens thrive between 1.2 – 1.8 mS/cm; fruiting crops like tomatoes sit closer to 2.0 – 2.4 mS/cm.
Pro tip: Temperature affects readings. Look for meters with automatic temperature compensation (ATC) so you’re not chasing ghosts on hot afternoons.
Grab the Right Toolkit
You only need three items to stay on top of EC:
-
Handheld EC meter – The Bluelab Conductivity / EC Pen is our gold-standard for accuracy and waterproofing. Budget starter? Check the AZ Waterproof EC & TDS Pen.
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2.76 mS/cm calibration solution – Keeps any meter honest. We stock the Aussie-made Flairform 2.76 Calibration Solution.
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Clean glass or plastic jar – For calibration and sample testing (never dip straight into nutrient bottles).
All of the above live in our Water Testing collection if you need to top-up supplies.
Calibrate in 60 Seconds
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Rinse the probe in fresh tap water, then shake off excess.
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Pour a small amount of calibration solution into your jar (never back-pour, it contaminates the bottle).
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Dip the probe, wait for the value to stabilise and press “CAL”. Your meter should lock onto 2.76 mS/cm within 15 seconds. If not, repeat or replace batteries/probe.
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Rinse again and you’re ready to test your reservoir.
If your EC readings keep drifting even after calibration, our Hydroponic pH Control in Australia: Simple Steps to Rock-Solid Reservoirs explains how unstable pH can throw EC out of whack—and how to lock both in at the same time.
Read, React, Repeat – Daily EC Routine
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Stir the reservoir to avoid stratified layers.
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Test & record the EC.
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Adjust:
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EC too high (above your crop’s target range) – Top up with plain, pH-balanced water.
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EC too low – Add concentrated nutrient solution slowly, retesting every minute.
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Re-check after 15 minutes; solutions take time to fully disperse.
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Log the final reading. Patterns over a week tell you if plants are drinking water faster than nutrients or vice-versa.
Quick-Reference Crop Targets
|
Crop |
Veg Stage (mS/cm) |
Bloom / Fruit (mS/cm) |
|
Lettuce |
1.2 |
– |
|
Basil |
1.4 |
1.6 |
|
Strawberries |
1.2 |
1.8 |
|
Tomatoes |
1.8 |
2.4 |
|
Capsicum |
1.6 |
2.2 |
Keep within ±0.2 mS/cm of these ranges for best results.
Troubleshooting Common EC Issues
|
Symptom |
Likely Cause |
Fast Fix |
|
EC climbs daily while water level drops |
Plants drinking water faster than nutrients (hot weather). |
Top-up with fresh water each evening; aim for original reservoir volume. |
|
EC falls but water level steady |
Plants absorbing nutrients faster than water. |
Increase base nutrient strength in 0.2 mS/cm increments. |
|
Fluctuating EC despite no changes |
Dirty probe or out-of-whack calibration. |
Clean the probe, recalibrate with 2.76 solution. Replace probe if >18 months old. |
Level-Up Monitoring (Optional Extras)
If you’d rather glance at a screen than manually test, upgrade to the Bluelab Truncheon Wand for quick dunk-and-read checks, or step into 24/7 tracking with the Bluelab Guardian WiFi Monitor (also in our Water Testing line-up). Automatic alerts let you correct issues before your plants even notice.
Final Word
Consistent EC is the backbone of healthy hydroponics. Log it each day, respond to what you see, and recalibrate weekly. Your plants will repay you with thicker stems, deeper roots and harvests you can brag about.
Need gear or advice? Swing by the Dr Greenthumbs Water Testing range or call our Wollongong crew on 1800 983 006. Happy growing! 🌱
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