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Go With the Flow

How water flow works and why it's needed in our aquariums.

By James B. Wood, Ph.D. |

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Water flow is needed in the wild and in our aquariums to keep most of our aquatic animals alive. Not only does water flow oxygenate the water, it brings food to organisms such as corals, stimulates growth and keeps sessile animals free of sediment. We take cues from the wild for our aquariums. If a coral lives in a high-energy environment in the wild, it is best to provide it with a high-energy environment in the aquarium. There are ways that you can provide adequate water flow for your aquatic animals, depending on your setup.

How Oxygen Gets into Water
Diffusion. If you ask most people how oxygen gets into water, they would tell you that one way is by diffusion. And they would be correct. Diffusion is the movement of a substance, such as oxygen, from an area of higher concentration to an area of lower concentration. The challenge is that diffusion happens at a molecular level and is very slow. How slow? In a series of lectures on the chemical features of water, M.N. Kutty (1987) explained how the solubility of oxygen in water is so small and the diffusion process so slow that it would take six years for oxygen to diffuse from the surface to a depth of 20 feet in still water. Almost all the dissolved oxygen diffusion in natural waters is assisted by some form of water motion.


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