An acute renal replacement therapy apparatus comprises at least two feedback control means (110, 120), each including an estimated volume calculation means (112, 122) arranged to calculate an estimated volume based on a set flow, a comparing means (114, 124) arranged to compare the estimated volume with a measured volume, a volume deviation determining means (114, 124) arranged to determine a volume deviation based on the result of the comparison, a correction calculation means (116, 126) arranged to calculate a correction amount based on the determined volume deviation, a flow control generation means (116, 126) arranged to generate a controlled flow control signal based on the calculated correction amount and the set flow, and a feedback control output means (118, 128) arranged to output the controlled flow control signal to a pump individually associated with each feedback control means and forwarding fluid from a fluid source and/or pulling fluid into a fluid sink and a flow correction distribution means (200) including an input means (210) arranged to input correction required signals calculated by and output from the correction calculation means in each of the at least two feedback control means, a limited correction signal calculation means (230) arranged to calculate a limited correction signal for each of the input correction required signals, and an output means arranged to output each calculated limited correction signal to the feedback control means from which its underlying correction required signal has been received.
