Nearly every aquaponics system utilizes a pump at some point in cycle. Some systems employ siphons in the grow beds, letting the pump run continuously, while others use a timer to toggle the pump on and off. Do you need a "pump controller" for continuous pumps? Absolutely! We've seen it too many times when siphons fail due to grow media or plant roots interfering, which leads to grow beds overflowing, tanks draining, fish loss and huge property damage. It might sound odd, but the true benefit of pump control is not so much to turn the pump on, but to shut it off.
This project kicks off a series on pump controls by starting with basics: time and relay control. Future projects include using simple moisture contact sensor (overflow sensor) to prevent overflows, advanced overflow sensors using XBees, depth sensing to prevent tank drains, using flow-rate meters to detect clogged pumps, and switching to backups.
Pump control, like any control systems, utilizes relays that connect to mains-level power and the usual warnings apply. Do not work on projects when the relays are under power (plugged into the wall). Use an enclosure for your relays to prevent accidental discharge and prevent water from hitting the electronics.