Will need to turn phone and the arduino on and off to save energy
Communication
Use a Motorola C168i controlled by Arduino via serial library to send text messages. Tutorial
Cost of sending international texts using Safaricom is approx. 11 cents/text. Safaricom Rates
Sensors
Dissolved Oxygen
Atlas Scientific Probe - They have sample arduino code. Calibration is good for atleast 12 months after initial calibration – $200
Ammonia
Ammonia probes are very expensive (>$400)
Instead, use Ammonia Alert Device coupled with a color sensor to determine concentration. Will need to place sensor close (< 3-4 mm) to the alert device and possible use a light source for accurate readings
Nitrate
pH
Atlas Scientific Probe - “Remember, a pH Sensor cannot be allowed to dry out or freeze. When it’s not in use keep it in the supplied soaker bottle. Periodically change out the storage solution in the soaker bottle with new storage solution. This pH Sensor can be fully submerged indefinitely.” – $106