An apparatus for and methods of control of a fluid flow. In a system for supercritical processing of an object, the apparatus includes a measuring device for measuring a pump performance parameter and a controller for adjusting a fluid flow in response to the performance parameter. The system further includes a processing chamber for performing a supercritical process and a device for circulating at least one of a gaseous, liquid, supercritical and near-supercritical fluid within the processing chamber. A method of control of a fluid flow includes the steps of: measuring a pump performance parameter; comparing a measured pump performance parameter to a predetermined target pump performance parameter; and adjusting a fluid flow in response to a difference in the measured pump performance parameter and the predetermined target pump performance parameter.