pH and EC are the two most important numbers in hydroponics. Get them right and plants thrive. Get them wrong and no amount of expensive nutrients or lighting will save your crop. This guide explains what pH and EC mean, why they matter, how to measure them accurately, and how to keep them in the right range.
What pH is in hydroponics
pH measures how acidic or alkaline your nutrient solution is on a scale of 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is alkaline. In hydroponics, the target pH range is 5.5 to 6.5 depending on the crop and system. Most nutrients are formulated to work within this window. Outside of it, nutrient lockout occurs and plants cannot absorb what is in the solution regardless of how much you feed them. pH drifts constantly as plants feed and as water evaporates. Different nutrients are available at different pH levels, which is why a stable range matters more than a single fixed number. pH that is too high causes iron, manganese, and zinc deficiencies. pH that is too low causes calcium and magnesium deficiencies.
What EC is in hydroponics
EC stands for electrical conductivity. It measures the concentration of dissolved salts in your nutrient solution, which is a direct indicator of nutrient strength. EC is measured in milliSiemens per centimetre. A higher EC means a stronger solution and a lower EC means a weaker solution. Seedlings and clones should be kept at 0.6 to 1.0 mS/cm. Vegetative growth runs at 1.2 to 2.0 mS/cm. Flowering and fruiting runs at 1.8 to 2.5 mS/cm. Late flowering flush drops to 0.0 to 0.5 mS/cm. Running EC too high causes nutrient burn and osmotic stress. Running it too low starves plants of the elements they need for growth.
How to measure pH and EC accurately
Accurate measurement requires a quality meter and regular calibration. Cheap meters drift quickly and give false readings that lead to incorrect adjustments. The Bluelab Combo Meter measures pH, EC, and temperature in one unit and is the most practical all-in-one option for most growers. The Bluelab pH and Temperature Pen is a compact dedicated pH pen for growers who already have a separate EC meter. The Bluelab Digital EC Meter is a dedicated conductivity pen for precise EC readings. The Bluelab pH EC Temperature Meter Bluetooth connects to the Bluelab app for logging and remote monitoring. The Apera pH and Temperature Pen is a waterproof option at a more accessible price point. The Heavy Duty EC Meter Waterproof suits growers who need a robust EC pen for daily use in wet environments.
How to calibrate your pH meter
Calibration is not optional. A pH meter that has not been calibrated recently will give inaccurate readings and lead to incorrect adjustments that damage your crop. Calibrate at least once per week during active grows and always use fresh calibration solution from sealed sachets.
- Rinse the probe with clean water and dry gently.
- Place the probe in pH 7.0 calibration solution and allow to stabilise.
- Adjust the meter to read 7.0.
- Rinse the probe and place in pH 4.0 calibration solution.
- Adjust the meter to read 4.0.
- Rinse and the meter is ready to use.
The Bluelab Probe Care Kit includes calibration solution, probe cleaner, and storage solution in one kit. Keeping the probe tip moist in storage solution between uses significantly extends probe life.
How to adjust pH
If pH is too high, add pH Down. If pH is too low, add pH Up. Always adjust in small increments and retest after mixing. GT pH Up and pH Down are precision pH adjustment solutions suitable for all hydroponic systems. Add pH adjustment solution to the reservoir while the pump is running to ensure even distribution. Never add pH Up and pH Down at the same time.
Automated pH and EC control
For larger systems or growers who want to remove manual testing from their routine, automated dosing systems monitor and adjust pH and EC continuously. The Bluelab pH Controller monitors pH and automatically doses pH Up or Down to maintain your target. The Bluelab Pro Controller Wi-Fi controls both pH and EC automatically with Wi-Fi connectivity and remote monitoring. The Bluelab Guardian Monitor Wi-Fi monitors pH, EC, and temperature continuously and sends alerts when values go out of range. The Bluelab PeriPods are peristaltic dosing pumps that work with the Bluelab Pro Controller for precise automated nutrient and pH dosing.
Testing soil and coco pH
For growers running coco or soil-based systems, measuring the pH of the medium itself is as important as measuring the solution going in. The Bluelab Soil pH Pen measures pH and temperature directly in soil and coco without needing to make a slurry. The Bluelab Pulse Meter measures EC, moisture, and temperature in the root zone via Bluetooth, giving a real-time picture of what is happening at the root level.
How often to test pH and EC
Test pH and EC at least once per day during active grows, before and after adding nutrients to the reservoir, and check runoff EC in coco and soil systems to monitor for salt buildup. Increase testing frequency during hot weather when evaporation raises EC faster. For the complete range of testing and control equipment available in Australia, browse the pH and EC Meters collection.