Article on flow in our aquariums

I am working on my penman skills & wrote this article today for our website.  Let me know what you think.
One of the key factors to maintaining successful reef aquariums is water flow.  Along with water quality and lighting, it is one of most important aspects of a healthy marine environment.  Before deciding on the amount and kind of flow you need, we need to talk about why flow is important in an aquarium.






 





Flow within an aquarium performs several tasks.  Your fish can chase down food when you feed your tank, but your attached invertebrates such as coral and anemones rely on the water currents to bring food to them.  After they eat and secrete their waste, they rely on the same current to carry the waste away.  Your tank needs adequate flow to keep this waste suspended until it can be removed by your filtration system.





 





Another important duty that water flow performs is the oxygenation of the water.  When the water rolls at the surface, or falls over your overflow, it releases its toxic carbon dioxide, and exchanges it for oxygen.  Without this exchange CO2 levels will rise, and oxygen levels will fall.





 





Strong flow stimulates coral growth and the health of your fish.  There have been countless times I have seen fish “riding” the water flow in tanks with strong flow.  It stimulates them to stay active and keeps them healthier.





 







How much flow do I need?

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This is the million dollar question, and a hotly debated topic.  Turnover is the amount of times your water is moved.  If you have a 40 gallon tank and want to turn it over 10 times an hour, you would need the pumps and powerheads to push 400 gph of water.  A SPS dominated tank needs a minimum of 60 times turnover, and once it is grown in, may need up to 100 times turnover.  Now if you try to add a big fleshy LPS coral, anemone, or leather to a tank with 100 times turnover, it may not last very long.  A fish only system may be fine with ten times turnover if you can keep dead spots from forming






What kind of flow do I need?
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Laminar flow is the straight flow created by many powerheads.  They shoot out a concentrated stream of water.  This results in the water flowing in the same direction and speed all the time.  This type of flow results in poor coral health and dead spots in the aquarium.



 



Turbulent flow is the flow we try to duplicate in our aquariums.  Turbulent flow may be strong in one direction for one minute and then strong in another direction, followed by very little flow.  It is always changing speeds and direction.



 



Surge flow is the rapid release of a large amount of water creating a very strong flow, followed by a period of low flow.  Think of it as waves crashing every 5 minutes on the beach.  This type of flow can be created by wave boxes, or a surge tank mounted above the aquarium.










How do I create optimal flow?
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Most powerheads create straight laminar flow, however when you direct them at each other, bounce the flow off the glass or a corner, the flow becomes very turbulent.  Add in features such as timers, speed control, rotators, and wave makers and you can turn your powerheads into a great tool to move water.  Some powerheads such as the Vortech’s and Tunze’s have controllers that will change the speeds automatically.



 




 




 



Another option for great flow is a closed loop.  This method turns your tank into swiss cheese by drilling holes in the sides and back of the aquarium.  Intakes suck water into the supply pipe to an external pump that pumps it back into the tank in various locations.  By adding valves to the outside, and loc line to the outlets you can constantly change the direction and amount of flow.  Make sure you have more then one inlet and protect them with screens.  This will protect both the pump, and your fish from getting sucked in.



 





Conclusion
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Now you realize how imperative good water flow is to the health of your aquarium.  There is no cookie cutter secret to success however.  It is up to you to decide what is best for your tank and the type of reef you keep, as well as what best fits your checkbook.