Above images from left to right are AZOO, Tetra, and API pH test kits.
The sample tested was a pH Standard 7 solution.
We dropped the reagent separately, mixing evenly after each drop, and waited for the color change.
The result of API’s kit is pH=7.6.
The result of Tetra’s kit is pH=7.5.
The AZOO’s kit is pH=7.0.
Finally, we used a digital pH meter to test the water sample confirming it was pH 7.0. The AZOO pH test was more accurate and easier to read than the other brands.