PROBLEM TO BE SOLVED: To provide a method for controlling an oxygen concentration dissolved in breeding water of a circulation type breeding aquarium.SOLUTION: A method for controlling an oxygen concentration dissolved in breeding water of a circulation type breeding aquarium is characterized as follows: the oxygen concentration dissolved in the breeding water is measured and a measured value (A) is acquired the measured value (A) is set as a control target value (B) a current value (A) of the oxygen concentration in the breeding water is measured and an oxygen feed rate is increased when the current value (A) is equal to or lower than the control target value (B) an operation of reducing the oxygen feed rate when the current value (A) exceeds the control target value (B) time duration (t) in which a time derivative value of the current value (A) becomes near 0 is compared with a predetermined value (t0) when the time derivative value is near 0 as a result of increasing the oxygen feed rate and it returns to initial control operation when t≥t0, and the oxygen feed rate is increased when t
