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WATER MOVEMENT IN REEF AQUARIA

If you have ever dived or snorkelled on a typical coral reef, it would become readily apparent that the water is in constant motion.
This constant water movement is vital to the corals, plants and invertebrates that inhabit coral reef areas. Water motion brings food to the reef inhabitants along with a constant supply of trace elements and minerals enabling the animals and plants to grow and prosper, also the removal of wastes, decaying tissues and detritus is accomplished at the same time.
The most dynamic water movement on a reef typically occurs within the first thirty feet. Most of the popular corals available to hobbyists are from this region.
It would be virtually impossible to duplicate the water motion found on a typical coral reef in the confines of the home reef aquarium. However, uni-directional currents produced by water pumps or power heads can create a pleasing and beneficial effect for the reef hobbyist.
The Reef environment is characterised by three types of water movement:
1)Surge. 2)Turbulence. 3)Laminar flow.
Surge is the back and forth movement caused by deep ocean swells and wind driven waves.
Turbulence is a random swirling of water in all directions produced by opposing currents, especially present around underwater objects ie. rocks and corals.
Laminar flow is water movement in a straight direction ( outward flow from a pump or power head) normally encountered in reef channels and used across the surface of reef tanks to “break” and ripple the water surface and aid in gas exchange.
To generalise, most corals will prefer or adapt to turbulent and wave style water movement. Aquarists are encouraged to replicate this turbulent or ebb and flow styles of water circulation. Few corals prefer laminar flow (straight direction) and many will not survive subjection to it. A random surging flow is far more natural and beneficial.
When estimating needs for water movement, it is important to remember that it is not the velocity of the water flow, but the total energy that is of importance. The total energy being the impact of movement within the aquarium. It is advisable to have pumps capable of turning the overall gallonage of the display aquarium over between 6-10 times per hour.
An electronic wave making device or pump controller can be invaluable in creating a random turbulent water flow within the aquarium. Some have a “night time calm” feature which disables the pumps at night.