The cabinet will display total dissolved solids (TDS) of the water in the reservoir. Note what the TDS is when you first fill the reservoir and try to maintain a TDS of 100-250 above that number. Add 2.75 oz. (80ml) of nutrients at a time, wait 15 minutes to adjust the TDS.
Viking
Owner manual PDF of Viking GCV12LSS - 24" Professional Under-Counter Micro Green & Herb Cabinet .