Dissolved Oxygen concentrations fall in summer... use extra aeration using airstones or venturi devices. Hi blow air pumps are ideal

Dissolved Oxygen Concentration (DOC) is the term given to describe the amount of oxygen that is dissolved in pond water.

• There are many factors that will affect DOC in a koi pond, some of which we can control, others we cannot, but can respond in a number of ways to guard against problems.
• Of course, dissolved oxygen is important to all life in a koi pond, not simply the fish, and they all have a demand on the finite supply of oxygen dissolved in the pond water.
• In relation to the activities of bacteria and other microscopic pond organisms, the oxygen demand by koi is not the greatest (but this will vary with stocking density).
• The range of DOC in a pond will run from a minimum (0mg/l) to a maximum (about 15mg/l), where even the supply of additional aeration would not change the DOC.
• Bacteria / Fungi The majority of bacteria in a pond are aerobic (requiring oxygen) being found in abundance in the filter.
• Fortunately, the plants, during the day, also add oxygen to the pond's oxygen budget in excess of what they require in the day. Oxygen Budget However, as most koi ponds are sparsely planted, particularly with oxygenating plants, then there is likely to be little oxygen added courtesy of the plant life.
• Effects of low DOC on fish Low DOC has very obvious affects on koi.
• Such units are common place in intensive aquaculture and can also be used to detect either a pump or air pump failure due to the associated drop in DO.
  
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