I must be searching for the wrong stuff, because I feel like these should be rather inexpensive?
What's the easiest route to take there on some pump that can be simply hooked to the arduino?
http://www.amazon.com/Vdc-Normally-Closed-Solenoid-Valve/dp/B007D1U64Ehttp://www.allelectronics.com/make-a-store/item/SOL-132/SOLENOID-VALVE/1.htmlHave not used one and comments on them vary, but sounds like what you want. You didn't provide much detail.
So I connect the relay module's VCC to the arduino's 5v out, and the relay module's GND to the arduino's GND out, right? Then, does each relay's COM pin get connected to the 12v on the power supply? So my power supply would need to be spliced 32 times!?
Indication LED's for Relay output status