Water Movement

Sessile invertebrates benefit from strong currents that wash away wastes and bring nutrients and oxygen to them. Fish get exercise by swimming against currents. Any saltwater aquarium benefits from all the water movement you can provide, as long as it is not so vigorous as to slosh water over the rim. The return pipe from the sump discharges water in one direction only, and in a continuous stream. Natural water movement on the reef is multidirectional and intermittent. You can simulate natural turbulence by installing powerheads in the display tank. Place at least one powerhead (see page 86) toward the back of the tank with the outflow directed so it intersects that from the return pipe. The perpendicular currents collide and create turbulence. Using two powerheads, controlled by a timer known as a wavemaker, is an even better idea, though certainly not essential. Wavemakers allow the powerheads to be switched on and off on a regular schedule, creating pulsed water movement. Alternating between the two powerheads causes the motion to come first from one direction then the other. Some wavemakers permit alternation between both powerheads on, both off, or only one or the other. This results in currents of varying strength and direction.

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