Others, such as pH, alkalinity, hardness and clarity affect fish, but usually are not directly toxic. Each water quality factor interacts with and influences other parameters, sometimes in complex ways. What may be toxic and cause mortalities in one situation, can be harmless in another. The importance of each factor, the determination method and frequency of monitoring depends upon the type and rearing intensity of the production system used. All biological and chemical processes in an aquaculture operation are influenced by temperature.
Fish adjust their body temperature and metabolic rate by moving into cooler or warmer water.
Each species has a preferred or optimum temperature range where it grows best. At temperatures above or below optimum, fish growth is reduced. Mortalities may occur at extreme temperatures. Solubility of oxygen increases as temperature decreases. In ponds, DO can change dramatically over a 24 hour period.