Julio,
Your link indicates that the motor came with a motor driver board. The data sheet can be found here...
http://www.sanyocomponentsdirect.com...K672-340-E.pdf
With stepper motors, you need some feedback mechanism that can sense position and speed and a direction command. For your motor, it will also need a pretty hefty power supply. An FRC battery could supply the needed power or certainly a 12 volt pack of D cells would work as well. In your application, a motion limit might work but something that can sense the actual fluid flow would be better. Then you would just need to command a direction and enable the motor. Disable when the motor reaches the required distance/flow.