Senno In Line DUAL TDS Meter with 1/4" quick connect fittings.
Detection range is 0-999 ppm, sensitivity is 1 ppm, accuracy is + - 2%.
Over 80% removal rate the indicator shows green flash, less than 80% show red flash.
Aquarium & Reef keepers should select post membrane (pure) as inlet and post DI as outlet.
Systems should be running making water prior to testing.