Different dkh readings

[Andrew Chan]

Hv been using Seachem's Reef Carbonate for 2 weeks. Just did a kh test, 1st using Aquarium Parmaceuticals Inc Test Kit which gave a reading of 14 dkh. At the same time, also used Aqumedi Test Kit and reading was 9dkh. Pl advise which reading should I follow?

[Tech Support JR]

Hard to say to be honest. Reef Carbonate is adding a source of carbonate alkalinity which should be easily measured by any test kit for alkalinity. Sometimes we do hear of cases where a test kit reports that it tests for KH (carbonate alkalinity) when it actually tests for total alkalinity. So, I would check to make sure each of the manufacture's test kit tests for actual carbonate alkalinty and not total alkalinity.

As a side note this issue would be avoided if either of the kits included a reference sample of known value to confirm that the reagents were giving good readings. You might have a look at some of our kits which all include references of known value.