A container arrangement is for fish farming and includes a body with a bottom section and a wall section that define a volume adapted to receive water for the fish farming. A water treatment arrangement is for treatment of the water in the container arrangement. The water treatment arrangement has a device for removal of CO2 from the water of the container arrangement including a separation chamber for CO2 and means for separation of CO2 arranged at the chamber. The water treatment arrangement is arranged in the body of the container arrangement.
