This paper presents the pH measurement system to construct a water spoilage prevention system for the fish culture in cement ponds, to reduce diseases in fish, and to reduce the problems of the death of fish. The objectives of this research were: 1) to design and construct a system for measuring pH values of water in the fish ponds via Internet of Things, and 2) to determine the efficiency of the pH measurement system. The study instruments were NodeMCU/ESP8266, pH electrode set and Netpie application. The results showed the efficiency of the pH measurement system starting from the first stage of water replacement in the cement ponds as follows: during day 1-15, the suitable pH value for normal living of freshwater fish was 6.002-8.489, and during day 16-19, the acidic value rose with pH 5.964-5.381. The results revealed that the system could display real-time pH values via Internet of Things using the Netpie application with Data Feed function.
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