A mixing apparatus for in-line mixing of fluids is described herein. In some embodiments, the mixing apparatus comprises a mixer body defining a plurality of support arms and a substantially conical flow member that can be coupled to the plurality of support arms. In other embodiments, the mixer body defines at least one body injection passage extending from an injection inlet on the exterior surface of the mixer body through one of the support arms; the flow member defines a flow member injection passage extending through at least a portion of the flow member to an injection outlet defined at the leading end or the peripheral surface of the flow member; and the flow member is coupled to the support arms such that the injection inlet is in fluid communication with the injection outlet via the mixer body injection passage and the flow member injection passage.