I realize this thread is ancient, but it popped up on a search.
I have an aquarium with a refugium (a second tank for filtering and introducing new members to the tank)
The bottom tank is gravity fed and the water is pumped back up the main display tank.
The issue for me was, how to cut-off the gravity flow in case of a power failure.. so I'm looking at electronic ball valves instead of solenoids (because the solenoid needs constant power to stay open).
For the ball valve:
To open the valve, you need power..
The close the valve, you need power with reverse polarity .(it doesn't close with a lack of power)
Here's how I'm going to tackle it (might seem brute force, but I"m pretty sure it will work)
I'm going to order a 4 channel 5v SainSmart physical relay controlled by an Arduino.
I'm going to feed a 3v line into the Arduino to detect a power failure (some cheap transformer)
The 4 channels will be configured in the following manner: + - - +
For "open" operations, I will open relays "1 and 2" (+ -)
For "close" operations, I will open relays "3 and 4" (- +)
After 15 seconds, I will close all relays, since it takes about 5-10 seconds to fully open the valve.
The only issue that could happen is if I get my wires crossed and open the wrong relays..
but this gives me total control..
Of course, the Arduino and corresponding power source to open/close the valve will need battery backup.
Will follow up