EC value understood and controlled: measure dissolved salts in mS/cm — seedlings 0.4–0.8, vegetative 1.2–1.6. Detect salt build-up and correct by flushing.
EC (Electrical Conductivity) measures dissolved salts in mS/cm or μS/cm. 1 mS/cm = 1000 μS/cm. TDS conversion: EC × 500 (0.5 scale) or × 700 (0.7 scale). Target values: Seedlings 0.4-0.8, vegetative 1.2-1.6, flowering 1.6-2.2 mS/cm. Too high EC leads to lockout, too low to deficiency symptoms.
The ideal EC value for cannabis seedlings is between 0.4 and 0.8 mS/cm.
You can measure the EC value using an EC meter by taking a sample of the nutrient solution and reading the value.
If the EC value is too high, you should rinse the system with clean water to wash out excess salts and lower the value.