When people come to the store wanting to build a pond from scratch, replace a malfunctioning pump or make the pond more maintenance-free I immediately go into my song and dance number — the famous if-it-were-me-I-would-install-an-external-pump routine! An external pump is the most important component to a pond system. It offers the pond-owner a less troublesome, longer-lasting, less expensive (in the long run) piece of equipment than a submersible pump that runs the same amount of gallons per hour.