I want clarify that would it be possible for me use this dc pump with my project without using a stepper motor.
You can use this.
You will need to control this with a relay or a MOS FET
You will need an external power supply for the motor.
You will need a diode 1N4007 across the motor terminals, reversed biased.
DC 3v to 6v submersible pump
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It's already got a motor.
You will need a motor driver (a transistor or MOSFET) if you want to control it with the Arduino.
Operating : 3v to 6v DC Power consumption: 0.4W to 1.5W
"Wost case" with 2.5W @ 3V that works-out to 2.5/3 = 830mA. So your driver circuit should be able to handle at least ~1 Amp.
[u]This solenoid driver circuit[/u] should work.
An opto coupled relay would be the easiest. 10 amps are plentiful for Arduino projects.
I switch exactly the same pump with a FET (overkill IRF3708), driven like DVDdoug suggested (I have an additional pulldown on the Arduino side).
just to let you know that if you use 12VDC, i will REALLY put out some flow !
maybe only for a few minutes (seconds??) till it burns out however.
I was super impressed at the one I bought after connecting it to 12VC. and am VERY lucky it did not burn out in that first 5 second test.....
using the CORRECT voltage will not be as impressive.
at 5volts, it is a decent pump and if you are watering plants, it will do that very well.