controlling speed of a motor

Hi. I have a pump running with a Arduino Uno+motor shield +9V battery.
I run couple of test, it works great but I would like to control the speed of the pump by adding a "regulator"> see photo attached. I tried to put it between the motor shield and the pump but it does not work..I was wondering if I need a special library to control that "regulator"...to make it work! thanks
My other idea might be to define that controlled on the analog pin, but I wonder how to deal with the 4 connector( see back picture) ( Power-, power+, Motor+, Motor-), how to define them?
Thanks!

Images from Original Post so we don't have to download them. See this Image Guide

...R

djeh1usa:
Hi. I have a pump running with a Arduino Uno+motor shield +9V battery.
I run couple of test, it works great but I would like to control the speed of the pump by adding a "regulator"

Why not just control the speed of the pump with the motor shield?

...R

9V battery? That's something you'll need to address first.

in fact, it turns out I can control the pump directly with the motor shield, without going through Arduino. (v battery was enough to start the pump...Only pb, I can not reverse the flow direction, I only control the speed of it.

djeh1usa:
in fact, it turns out I can control the pump directly with the motor shield, without going through Arduino.

As you have not told us how you are doing that I, for one, have no idea how to help you.

...R