A device for the mixing of a gas into a liquid comprises a hollow frustum shape housing having a central axis, extended from a small diameter fluid outlet end, defining a fluid outlet opening, to a large diameter end; a liquid inlet port positioned adjacent the large diameter end is formed in said housing which allows delivery of pressurized liquid into said hollow housing, and a helically cut conical member is positioned and affixed within the hollow center of the housing with its axis aligned with that of the hollow frustum shape housing such that fluid delivered into the housing forms a swirling motion around the outside of the conical member as it passes from inlet port to outlet opening. The housing has a gas inlet for delivery of gas to the fluid within the frustum shaped housing at a position adjacent to the fluid outlet opening as the fluid moves from inlet to fluid outlet opening.