Some pH movement is normal as plants take up water and nutrients. Rapid or repeated drift usually signals a measurement, water chemistry, mixing, reservoir, or root-health issue.
Diagnosis
- Calibrate the pH meter with fresh reference solutions and verify the reading with a second method if possible.
- Test source-water alkalinity and record pH before and after adding nutrients.
- Mix nutrients completely before making small pH corrections.
- Check whether a small reservoir, heavy plant demand, algae, or unhealthy roots are driving rapid change.
Stabilising the system
Use a larger working volume where practical, top up consistently, keep light out of the reservoir, and record readings at the same time each day. Avoid repeated large corrections without identifying the cause.