What is "powerhead"

n. 1 The part of a machine that is the source of power 2 A small pump used in aquariums 3 A bangstick; a kind of underwater firearm

A powerhead, bang stick, smokie or shark stick is a specialized firearm used underwater that is fired when in direct contact with the target, not to be confused with other types of underwater firearms which fire specially designed projectiles and do not require direct contact with the target. Powerheads are often used for spear fishing and against sharks or alligators for sport, defense, or to kill nuisance animals. The term powerhead refers to the firearm-like part of the device; when attached to a shaft to form a spear, it may be referred to as a bang stick or shark stick. The spear in question may be handheld or launchable from a spear gun.

An aquarium powerhead is a water pump completely submerged into an aquarium to circulate water; usually this is used to create flow throughout the tank. For example a single powerhead could be used at one end of a freshwater aquarium to simulate a laminar river current, or multiple powerheads can be positioned throughout the aquarium to create more turbulent flow. A switching or variable-voltage system (also known as a "wavemaker") is commonly used in reef aquaria to more closely simulate the movement of ocean water. Water circulation is vital to proper biological filtration of most saltwater aquaria (particularly those using the Berlin Method), and is useful in freshwater aquaria for allowing free-swimming fish adequate exercise.