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Gas Chemistry
Dissolved Oxygen
The amount of oxygen gas dissolved in water - the fundamental requirement of aquatic life.
Unit: ppm or mg/L Code: DO
📖 Overview
Fish need oxygen. In cool water, dissolved oxygen can reach 12+ ppm. In warm water, saturation drops. In aquariums, agitation from filters and airstones drives gas exchange at the surface. Poor circulation, high temperatures, overstocking, and decaying organics all deplete oxygen. Fish gasping at the surface are usually oxygen-starved, not gasping for atmospheric air.