Short answer: not strictly. Following the label rate carefully can grow a good crop, and UF/IFAS treats a meter as optional for Kratky growing. But a meter is the only way to know the real strength of your solution, and it makes problems far easier to diagnose.
Growing without a meter
- Use a complete hydroponic nutrient.
- Measure doses accurately, ideally with a syringe or small scale.
- Mix at the label rate for hydroponic or non-circulating systems.
- Know your water: very hard water may make the label rate too strong.
What a meter tells you
- Your water’s starting point. Hard water can carry a large share of your target strength before you add anything.
- Whether you mixed correctly. A quick check catches a missed part or a doubled dose.
- What is happening later. Measuring the remaining solution tells you whether to top up with water or with solution.
- Whether a symptom is a strength problem. Without a reading, pale or burnt leaves are guesswork.
EC or TDS?
Both measure conductivity. EC meters show mS/cm or µS/cm, which is the same on every meter. TDS or PPM meters convert using a 500 or 700 scale, so check which yours uses before comparing to charts.
Features worth having
- Automatic temperature compensation
- Readings in EC, or a selectable PPM scale
- Easy calibration, with a standard such as 1.41 mS/cm (Oklahoma State University Extension)
Related guide: supplies for mixing Kratky nutrient solution.
Sources
- University of Florida IFAS Extension. Set It and Forget It Hydroponics (HS1488).
- Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).
