When fish are reared in a static pool of water, control of environmental factors affecting their growth and health is much reduced over the use of flowing water technology. Dissolved oxygen (DO), rather than being a steady component of the water supply, changes radically following a 24-hour cycle of photosynthesis and respiration. Fish are the only consumers of dissolved oxygen in flowing water systems, but in static water fish are a minor component of a complex oxygen budget. Water temperatures usually vary with the season since they are controlled by ambient air temperatures. Thus, static water aquacultures have a particular growing season based on a chosen fish species' temperature tolerances and seasonal surface water temperatures.