Wednesday, May 30, 2007

Should I have a constant concentration of salt in the pond? If so, what concentration? -Glenn

The only time salt is absolutely needed is when your Koi have a parasitic infestation. Salt hurts freshwater parasites because they are used to living in a saline-free environment. Salt irritates Koi, so it makes them produce a thicker slime coat. Some people keep a low level of salt in their ponds to help their Koi osmoregulate too.

From the Wikipedia article: Osmoregulation is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the body's water content; that is it keeps the body's fluids from becoming too dilute or too concentrated. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution the more water wants to go into the solution. The pressure that must be exerted on the hypertonic side of a selectively permeable membrane to prevent diffusion of water by osmosis from the side containing pure water.

Animals in all environments (aquatic and terrestrial) must maintain the right concentration of solutes and amount of water in their body fluids; this involves excretion: getting rid of metabolic wastes and other substances such as hormones which would be toxic if allowed to accumulate in the blood via organs such as the skin and the kidneys; keeping the water and dissolved solutes in balance is referred to as osmoregulation.

If you want to keep a low level of salt, add one pound of rock salt per 100 gallons of water.

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