To best simulate natural water movement in your reef aquarium, you must first understand the three main types of water movement.
Powerheads, while relatively inexpensive, produce only laminar currents. If you choose to implement a powerhead, do not aim water flow directly at invertebrates - the flow may be too intense and organisms may suffer damage. You can, however, direct flow to a specific area to reduce detritus buildup. Depending on your aquarium setup, you can create multi-directional flow with a powerhead by adding PVC pipe and fittings to the outflow.
Oscillating powerheads rotate within the aquarium and direct water over a wider area. By implementing several of these devices, you can create a turbulence pattern similar to that found on a reef.
Electronic wavemakers may be used with multiple standard or oscillating powerheads to produce turbulence by shutting the powerheads off and on in random fashion.
Water flow diverters, installed on the return of your main filtration, contain a pressure activated switching valve that acts as an alternating tee, splitting your return line into two separate outputs to create beneficial currents. If your aquarium is large, you can use more than one valve after the tee to create several currents.
Important water flow considerations
While good water movement is critical for the health of your reef aquarium, too much water movement can be unhealthy. If current is too strong in a particular area, corals will grow around that spot. While inhabitants generally adapt to water movement patterns, you must pay close attention to the growth and development of your reef system, and adjust water flow to levels under which inhabitants thrive. With proper planning and equipment, you can easily create healthy water motion within your aquarium.
Michael Paletta is the author of two books, "The Modern Marine Aquarium" and "Ultimate Reefs," and has acted as a consultant with the National Aquarium in Baltimore and the Pittsburgh Zoo Aquarium.