Aquarium Answers Water Flow | Marineland

Reef tanks need higher flow so water is moving in all areas of the aquarium
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Some specialized systems require specific water flow patterns. Jellyfish and other plankton are best-kept in kreisel aquariums, which have a specialized gentle laminar water flow that keeps the animals suspended and away from the sides of the tank. On the opposite extreme, a friend of mine was conducting research on an endangered species of freshwater goby that lived in mountain streams with a high flow rate. He used an electric outboard boat engine to maintain a high water flow rate in a special oval raceway aquarium with plenty of rocks and turbulence.
The most common type of water movement in the reef aquarium is laminar flow. This simply means that the water is moving in one direction.
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These filters are super popular in the freshwater hobby. However, they are rarely seen in the marine hobby. That may be changing as more and more hobbyists venture into the world of nano tanks. These items are great for producing water flow (especially along the surface) for small aquaria. The  is easily positioned in the aquarium and has an adjustable flow rate. The venturi system can also be used to aerate the water.
Photo provided by FlickrI made this video talk about proper water flow in a reef aquarium now these needs will be different for everybody
Photo provided by FlickrWater Flow in the Marine Aquarium - Blue Zoo Aquatics
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We want the flow to come from the back of the aquarium on top, slight ripple but not breaking the surface of the water, and move to the front glass, down the glass to the plant surface (substrate), and then across the plant surface to the back glass and up the back glass to create a circular front to back flow. This will contact the tiny foreground plants as well as the rest with CO2 and nutrients, and keep ammonia pockets from forming in otherwise dead spots which then attract algae.As predominantly sessile animals, reef invertebrates arecritically dependent on specific water movements to not only help themthrive, but to survive in oceans and aquariums alike. Proper water flowserves many purposes including but not limited to the following: thecarriage of food and other nutrients to a coral, the carriage of wasteproducts away, the exchange and dispersion of sexual cues and gametes,purges suffocating detritus, disperses and dilutes familiar and alienallelopathic compounds, and stimulates and supports new growth.Proper water flow is crucial for success with reefinvertebrates. However, it is an often neglected and surprisinglyinflexible parameter for coral health. Water movement is one of thethree fundamentals in reef aquarium husbandry along with light andfood. Fortunately, it is also the least controversial dynamic and avery straightforward and simple endeavor. While inadequate lighting ofsymbiotic corals can often be compensated with extra feeding,inadequate water flow is categorically limiting to growth and increasesthe risk of morbidity.One of the most important things to consider when choosing the filter for your aquarium is the filter flow rate. Great filter flow rate and efficient water movement throughout the aquarium are key to maintaining healthy environment for your fish.It is very difficult to create too much water flow inmost reef aquariums given the very dynamic environment that most coralshail from, but it is possible to dispense water flow improperly.GPH stands for “gallons per hour,” which in general refers to the flow rate of filters. It shows the maximum number of gallons of aquarium water flowing through a filter in one hour. Based on filter strength, filter type, efficiency, and state, the GPH greatly varies.