Total Dissolved Solids Significance to Fish and Aquatic Life

In bodies of water, like rivers, higher levels of total dissolved solids often harm aquatic species. The TDS changes the mineral content of the water, which is important to survival of many animals. Also, dissolved salt can dehydrate the skin of aquatic animals, which can be fatal.

Concentrations that are too high or low can affect the fish’s growth or cause death. A level of 400ppm is recommended for most freshwater fish.

Some fish are adapted to living in more saline waters and a few species of fresh water forms have been found in natural waters with high dissolved salt concentrations of 15,000 to 20,000 mg/L. Fish can become acclimatized slowly to higher salinities than those to which they are accustomed, but fish in waters of low salinity cannot survive sudden exposure to high salt concentrations such as those resulting from discharges of oil well brines.

Among inland waters in the United States supporting good mixed fish fauna, about 5% have a dissolved solids concentration under 72 mg/L, about 50% under 169 mg/L and about 95% under 400 mg/L.

Finally, dissolved solids may influence the toxicity of heavy metals and organic compounds to fish and other aquatic life. This takes place primarily because of the antagonistic effect of hardness on metals. Chromates, coppers, cyanides, detergents, phenolic compounds, zinc and several other substances are generally more toxic in distilled water than in hard water of high dissolved solids.

Chemical Water Quality Parameters
Electrical Conductivity of Water
pH of Water
Relation of Acidity and Alkalinity in Water
Primary Anions and Cations in Water
Dissolved Gasses in Water
Primary Nutrients in Water and Eutrophication
Toxic Constituents in Water
Pesticides in Water
Oil in Water

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Physical Water Quality
Chemical Water Quality
Biological Water Quality
Water Basics 101