TDS metre and conductivity metre
Instruments that measure total dissolved solids (TDS) or conductivity of water. Essential for monitoring the quality of osmosis water.
Detailed explanation
The TDS metre (Total Dissolved Solids) measures the total concentration of substances dissolved in water in parts per million (ppm). The conductivity metre measures electrical conductivity in microsiemens (uS/cm).
The two measurements are correlated: TDS = conductivity x conversion factor (typically 0.5-0.7).
Main uses: verify the quality of osmosis water (target: 0-5 TDS), monitor remineralization (variable target), control the approximate salinity in brackish water.
Cheap TDS metres (10-20 euros) are sufficient for aquariums. They must be calibrated with standard solution periodically.
For monitoring shrimp aquariums, the TDS metre is essential: even small variations in TDS can stress sensitive Caridina.