jremington:
1.8 Ohms sounds reasonable, in which case the start/stall current, operating from a 12V supply, would be around 6.7 Amps. A 10 Amp motor driver should work.Or, follow this tutorial for a MOSFET driver http://bildr.org/2012/03/rfp30n06le-arduino/
Contrary to the advice given in that tutorial, you should use a logic level MOSFET, like the one recommended.
Ok so the tutorial makes good sense and all. Now On one of the motors I need to be able to connect the Optical sensor to the Single-head pump. This is what will controll on/off. So I would need to run the sensor in-line with the mosfet between the gate and the arduino?