Using low voltage DC pumps is a safer way to become involved in flow control. Direct Current (DC) is generally simpler to control than Alternating Current (AC) and the low voltages are much safer than the 120 volts AC coming out of a wall outlet.
Your DC pump will have two leads and the proper polarity must be observed. That means that the positive and negative connections must not be swapped. DC pumps come in two styles: brushed and brushless. Most newer pumps are brushless. A primary advantage of a brushless motor is that it is normally quieter and generates less electrical interference. However, because the motor generally incorporates an electronic controller, it can be damaged if the power leads are reversed. So be careful. By contrast, reversing the power leads on a brushed motor pump will usually only cause the pump to not run properly (the motor will run backwards), but not cause damage.
To power the motor a source of DC at the proper voltage and supplying enough current is needed. Often this can be as simple as a “wall wart.”
More reliable industrial power supplies are also available. Use a power supply that can provide at least as much current as your pump needs. A greater current capacity is not a problem. This means that if, for example, your pump is rated 12VDC @ 0.5A, a 12VDC power supply with 10A capacity is perfectly safe. However a 24VDC supply rated for 0.5A may cause the motor to run too hot and eventually burn up.
You will also need a method to turn the motor on and off. Most small low voltage DC pumps can be controlled directly from a switch.