Most hydroponic growers use a pH meter or test kit and an EC or TDS meter. These two readings tell you whether the solution is in range for the plants.
pH Meter or Test Kit
A pH meter is quick and precise once calibrated. A test kit is cheaper but needs more care to read accurately.
EC or TDS Meter
An EC meter measures conductivity directly. A TDS meter gives a related reading. Either shows how strong the solution is.
Care
Calibrate meters as the maker recommends and store probes in the storage solution provided, not plain water.
Related guide: Supplies.
