Mount the device and sensors

Do this before you fill the reservoir: the water level sensor goes under the tank.

Glue the water level sensor to the underside of the reservoir. Choose a flat spot that stays straight when the tank is full. Which glue to use and how to place it: Water level sensor.
Choose a place for the control unit. It must stay dry, out of direct sunlight, and within cable reach of the sensors and the supply tanks. Fix the bracket with screws or double-sided tape (prepare the surface first), then slide the unit onto it.
Put the pH, EC and water temperature sensors in the reservoir. Clip them to the sensor platform and fix the platform to the tank with its magnets or suction cups. The probes must stay under water at all times.
Connect the sensors to the control unit. The pH sensor uses the round BNC connector. Do not touch its centre pin: the circuit behind it is sensitive to static electricity. See pH.
Plug in the power supply. Use the supplied 12 V adapter, or one that meets Specifications. The logo lights up bright, with a short dark pause every few seconds: the device is waiting for its Wi-Fi settings.

The air temperature and humidity sensor is built into the underside of the control unit, so there is nothing to mount for it.