|TDS Meter and Calibration Solution|
Tap: 236 ppm
RO: 8 ppm
RO w/crushed coral: 72 ppm
Tanks: 59 ppm (lowest) - 133 ppm (highest)
My tanks are not in the range above due to the use of RO water primarily for water changes and top offs, but now I will gradually add tap water to bring the TDS up.