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Aquaria Information from |
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Aquaria Information from |
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| WATER QUALITY |
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OSMOREGULATION IN FRESHWATER FISH |
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...or, why we salt our freshwater fish Osmoregulation is basically the maintaining of a proper fluid-electrolyte balance in the body fluids of fish. Osmosis is the tendency of water to travel through a semi-permeable membrane from an area of high electrolyte concentration. Why is this important to the fish? First of all, blood and body fluids contain several electrolytes. For ease in discussion, we will say salts. The concentration of salts in the body fluid of freshwater fish is much higher than their surrounding water. A fishes' gills are a perfect example of semi-permeable membrane. Water from the outside wants to go through the gills- to inside- and does, in large quantities. If this went on unchecked, the internal body fluids of the fish would become severely diluted and suffer an intolerable electrolyte loss through elimination. Freshwater fish deal with this problem in several |
ways. When there is plenty of oxygen in the water, they cut down on respiration and cut water influx through the gills. (This is one area where low dissolved oxygen can cause a fish a lot of problems). The other way fish deal with this problem is through cells clustered around the base of their gill filaments. These are called chloride cells. These cells require energy from the fish to work. They can transport sodium and chloride ions (against the flow, so to speak) from the water outside, to the blood inside. This replaces electrolytes lost by the production of the large amount of urine excreted. If there is too little sodium and too few chloride ions in the water, the chloride cells must work too hard to do their job, which causes more stress on the fish. This is why it is a good idea to add one teaspoon of sodium chloride (salt) to each gallon of water. This level of salt also kills some parasites, such as chilodonella and nocylodenella. |
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WATER QUALITY PARAMETERS ALL fresh water tropical fish: pH: 6.8-7.0 Salt: 1 teaspoon per gallon of water. Adding this amount of electrolytes to the fishes' environment is supportive to their efforts to maintain proper fluid electrolyte balance in their bodies (refer to our osmoregulation article). Goldfish: Domestic and imported, and aquatic specialties, newts, frogs, snails, crayfish, etc. pH: 6.8-7.0 Salt: 1 teaspoon per gallon of water under normal conditions, 2 teaspoons per gallon if stressed. African cichlids and brackish water fish: pH: 7.2, Salt: 2 teaspoons per gallon of water Salt water fish: pH: 8.0 Salinity: 1.019 Marine invertebrates: pH: 8.0 Salinity: 1.023 |
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