The present invention relates to a water oxygenation system, especially for fish farms, as well as a corresponding method. The system includes a water pump (1) connected to a pipe (2) with an output in the upper part of a vertical mixing column (3), the pump being configured to pump water into said column. The upper part of the mixing column also including a connector (4) for receiving oxygen from an oxygen supply, the column being configured to have a gas pocket (12) in said upper part, and wherein the lower part includes an output pipe (5) leading oxygenated water to a receiver tank such as a fish tank. The upper part of the column includes a gas outlet connected to a gas pipe (7), the gas pipe being connected to a controlled valve (6) and to said water outlet, thus being configured for controlled supply of gas from said gas pocket to said water outlet for increasing the oxygen level at the water outlet.