Atlas scientific makes really nice sensor kits that can be used with an arduino and similar boards.
You can connect multiple sensors using I2C and send it using MQTT and wifi form a nodeMCU to for instance NodeRED.
You can download our example sketch that implements MQTT and has a basic function for dissolved oxygen.
See the example pH i2c code by atlas scientific for more information on the pH sensor and the example i2c code for the dissolved oxygen sensor for more info on that one.
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