Powerheads are small electrical motors incorporating an impeller, a small propeller device driven by the motor, capable of pumping water. Their primary role is simple - they move water.

Powerheads come in a wide range of sizes, usually measured by the amount of water that they can pump in one hour. Most have adjustable flow rates so always choose one of a slightly larger throughput that you require - you can always turn it down. The more powerful powerheads are capable of pumping water vertically over four feet. This makes them ideal for returning water from a sump filter or for powering undergravel filters in deeper tanks where the flow from an airpump maybe insufficient.

Other uses for powerheads include producing tank currents via strategic positioning within the tank or creating additional surface agitation by locating them near the aquarium surface. Some powerheads also incorporate a venturi, a small pipe which allows air to be drawn into, and mixed with the water outlet of the powerhead to aid oxygenation. This can make their otherwise silent operation noisy but still comparatively quieter than a conventional airpump.

As most powerheads use tank water for cooling the motor, they must always be submerged however most models have a directable out flow and the ability to attach pipes or spraybars allowing flexible placement of the unit and control of the outflow.