Hi,
I made a quick search and found out that most hobbyist NH3 test kits are not very sensitive. The best I could find are the LaMotte 7418-02 (0,03 ppm NH3) and 3304 (0,06 ppm NH3) kits. The 3304 is designed to be used in saltwater only, the 7418-02 is for both fresh- and saltwater.
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