Everyone loves waves! Fish love to swim in them. Corals rely on them to have a healthy life. The waves are also responsible for stirring up the detritus in your tank. Another purpose for circulation is gas exchange. In a stagnant tank you will have extreme oxygen depletion. The more flow you have the less CO2 your tank will have present in the water column.
There are plenty of choices for circulating water. Closed loop systems are when you have an external pump plumbed into the glass, which eliminates powerheads. Powerheads are small(ish) water pumps that send water in a wide stream, some can be controlled with wave makers. Wave makers are timer-like devices that trigger powerheads on and off, which creates a wave motion. Another form of wave maker is a surge device. This can be as simple as a Dump Bucket that fills up and tips over, periodically dumping water into the tank. A more complex form of surge device is a Carlson Surge Device, which is essentially the same concept as a toilet bowl. The bucket fills and the water siphons (or flushes) out into the tank until the water level drops, which then breaks the siphon and resets the process. A Reverse Carlson is a submersed version that uses air rather than water and shoots a burst of water INTO the device instead of out of it, which has a very distinct BANG! There is also a Borneman Surge Device, which uses a toilet flapper. When the water fills up, a float rises with it and releases the flapper. This creates the effect of actually flushing a toilet, only it happens all day. There are all kinds of other devices that make different effects. You can't use EVERY type of wave technique, but you can mix a few.
What is your preferred method of tossing around your corals?
